diff --git a/package.json b/package.json
index 57345860..0adef5c1 100644
--- a/package.json
+++ b/package.json
@@ -51,10 +51,10 @@
   "jest": {
     "coverageThreshold": {
       "global": {
-        "statements": 62,
-        "branches": 61,
-        "functions": 70,
-        "lines": 62
+        "statements": 64,
+        "branches": 65,
+        "functions": 71,
+        "lines": 65
       }
     },
     "transformIgnorePatterns": [
diff --git a/src/components/Toolbar.js b/src/components/Toolbar.js
index b517f20c..ef27461b 100644
--- a/src/components/Toolbar.js
+++ b/src/components/Toolbar.js
@@ -3,6 +3,28 @@ import PropTypes from 'prop-types'
 import 'bootstrap/dist/css/bootstrap.min.css'
 import { compareVersions } from 'compare-versions'
 import styles from './Toolbar.module.css'
+import { toast } from 'react-toastify'
+import Config from '../config'
+import { getLinkAsButton } from '../utilities/uiUtils'
+
+const helpToast = (
+  <div >
+    <h2 className='text-primary'>Help</h2>
+    View or submit feedback to our {getLinkAsButton(Config.REPO_URL, 'GitHub repository')}:
+    <div>
+      {getLinkAsButton(`${Config.REPO_URL}/issues`, 'Issues (bugs or feature requests)', 'View/submit bugs or feature requests', true)}
+      {getLinkAsButton(`${Config.REPO_URL}/discussions`, 'Discussions', 'View/submit discussions', true)}
+    </div>
+    <br />
+    <h4>Getting started</h4>
+    Use this tool to create metadata files based on {getLinkAsButton(Config.AIND_DATA_SCHEMA_REPO_URL, 'aind-data-schema')}
+    &nbsp;&#40;{getLinkAsButton(Config.AIND_DATA_SCHEMA_READTHEDOCS_URL, 'readthedocs')}&#41;.
+    <ul>
+      <li>Select a schema from the dropdown. The latest version will be loaded as a fillable form.</li>
+      <li>Or, use the &apos;Autofill from file&apos; button to load an existing metadata file (must be JSON).</li>
+      <li>The submitted metadata will be validated and saved as a JSON file to your device.</li>
+    </ul>
+  </div>)
 
 function Toolbar (props) {
   /**
@@ -35,6 +57,14 @@ function Toolbar (props) {
     event.target.blur()
   }
 
+  const showHelpPopup = (event) => {
+    toast(helpToast, {
+      toastId: 'help-toast', // provide id to disable duplicates
+      autoClose: false
+    })
+    event.target.blur()
+  }
+
   return (
     <div>
       <select
@@ -66,6 +96,14 @@ function Toolbar (props) {
           </option>
         ))}
       </select>
+      <button
+        title="Get help"
+        type="button"
+        className={['btn', 'btn-default', styles.btnRight].join(' ')}
+        onClick={showHelpPopup}
+      >
+        Help
+      </button>
       <button
         title="Autofill with existing data from local file"
         type="button"
diff --git a/src/components/Toolbar.module.css b/src/components/Toolbar.module.css
index e8805a0d..ee7902b4 100644
--- a/src/components/Toolbar.module.css
+++ b/src/components/Toolbar.module.css
@@ -7,5 +7,6 @@
 
 .btnRight {
     float: right;
+    margin-left: 5px;
     color: navy;
 }
\ No newline at end of file
diff --git a/src/components/Toolbar.test.js b/src/components/Toolbar.test.js
index 1c4b274e..0c5a636d 100644
--- a/src/components/Toolbar.test.js
+++ b/src/components/Toolbar.test.js
@@ -4,9 +4,11 @@ import Toolbar from './Toolbar'
 import { parseAndFilterSchemas } from '../utilities/schemaFetchers'
 import sampleSchemaLinks from '../testing/sample-schema-links.json'
 import sampleSortedVersionListInstrument from '../testing/sample-sorted-version-list-instrument.json'
+import { toast } from 'react-toastify'
 
 const nullCallback = () => { }
 const sampleSchemaList = parseAndFilterSchemas(sampleSchemaLinks)
+jest.mock('react-toastify', () => ({ toast: jest.fn() }))
 
 describe('Toolbar component', () => {
   it('renders appropriate inputs on default', () => {
@@ -21,9 +23,11 @@ describe('Toolbar component', () => {
     expect(screen.getByTitle('Select a schema')).toBeInTheDocument()
     expect(screen.getByTitle('Select a version')).toBeInTheDocument()
     expect(screen.getByTitle('Autofill with existing data from local file')).toBeInTheDocument()
+    expect(screen.getByTitle('Get help')).toBeInTheDocument()
     expect(screen.getByTitle('Select a schema')).toBeEnabled()
     expect(screen.getByTitle('Select a version')).toBeDisabled()
     expect(screen.getByTitle('Autofill with existing data from local file')).toBeEnabled()
+    expect(screen.getByTitle('Get help')).toBeEnabled()
   })
 
   it('calls ParentTypeCallback and enables version selection dropdown when a schema type is chosen', () => {
@@ -86,4 +90,36 @@ describe('Toolbar component', () => {
     fireEvent.click(screen.getByTitle('Autofill with existing data from local file'))
     expect(mockRehydrateCallback).toHaveBeenCalled()
   })
+
+  it('displays a popup with Help info when the Help button is clicked', () => {
+    const expectedHelpDiv = expect.objectContaining({
+      type: 'div',
+      props: {
+        children: expect.arrayContaining([
+          expect.objectContaining({
+            type: 'h2',
+            props: expect.objectContaining({ children: 'Help' })
+          }),
+          expect.objectContaining({
+            type: 'h4',
+            props: expect.objectContaining({ children: 'Getting started' })
+          })
+        ])
+      }
+    })
+    const expectedToastParams = {
+      toastId: 'help-toast',
+      autoClose: false
+    }
+    render(<Toolbar
+      ParentTypeCallback={nullCallback}
+      ParentVersionCallback={nullCallback}
+      selectedSchemaType=''
+      selectedSchemaPath=''
+      schemaList={sampleSchemaList}
+      handleRehydrate={nullCallback}
+    />)
+    fireEvent.click(screen.getByTitle('Get help'))
+    expect(toast).toHaveBeenCalledWith(expectedHelpDiv, expectedToastParams)
+  })
 })
diff --git a/src/config.js b/src/config.js
new file mode 100644
index 00000000..5870a311
--- /dev/null
+++ b/src/config.js
@@ -0,0 +1,7 @@
+const Config = {
+  REPO_URL: 'https://github.com/AllenNeuralDynamics/aind-metadata-entry-js',
+  AIND_DATA_SCHEMA_REPO_URL: 'https://github.com/AllenNeuralDynamics/aind-data-schema',
+  AIND_DATA_SCHEMA_READTHEDOCS_URL: 'https://aind-data-schema.readthedocs.io/en/latest/'
+}
+
+export default Config
diff --git a/src/config.test.js b/src/config.test.js
new file mode 100644
index 00000000..f9eaf830
--- /dev/null
+++ b/src/config.test.js
@@ -0,0 +1,7 @@
+describe('config', () => {
+  it('has all required properties', () => {
+    const Config = require('./config').default
+    expect(Config.REPO_URL).toBeDefined()
+    expect(Config.AIND_DATA_SCHEMA_REPO_URL).toBeDefined()
+  })
+})
diff --git a/src/custom-ui/CustomWidgets.js b/src/custom-ui/CustomWidgets.js
index 0d309c77..1c3de928 100644
--- a/src/custom-ui/CustomWidgets.js
+++ b/src/custom-ui/CustomWidgets.js
@@ -6,7 +6,6 @@ import CheckboxWidget from '@rjsf/material-ui/lib/CheckboxWidget/CheckboxWidget'
 import TextWidget from '@rjsf/core/lib/components/widgets/TextWidget'
 import React, { useLayoutEffect } from 'react'
 import PropTypes from 'prop-types'
-import { toConstant } from '@rjsf/utils'
 
 const CustomTimeWidget = (props) => {
   const onChange = (selectedDate) => {
@@ -46,27 +45,35 @@ const CustomCheckboxWidget = (props) => {
 /**
  * Custom text widget to enable custom behavior for constants.
  * If const, update formData value to const value using onChange callback, render as readonly (grayed out)
+ * If null const, return null (do not display text input)
  * Otherwise, return default text widget
  * @param {*} props RJSF widget props
  * @returns A custom text widget
  */
 const CustomTextWidget = (props) => {
+  const { schema, onChange, value } = props
   // useLayoutEffect to run effect runs before browser repaints screen (reduce flickering)
   useLayoutEffect(() => {
-    if (props.schema.const !== undefined) {
-      props.onChange(toConstant(props.schema))
+    if (schema.const !== undefined && value !== schema.const) {
+      onChange(schema.const)
     }
-  }, [props])
-  return <TextWidget {...props}
-    readonly={props.schema.const !== undefined ?? props.readonly}
-    value={props.schema.const !== undefined ? toConstant(props.schema) : props.value}
+  }, [onChange, schema.const, value])
+
+  if (schema.const === null) {
+    return null
+  } else if (schema.const) {
+    return <TextWidget {...props}
+    readonly={true}
+    value={schema.const}
   />
+  } else {
+    return <TextWidget {...props}/>
+  }
 }
 CustomTextWidget.propTypes = {
   value: PropTypes.any,
   onChange: PropTypes.func,
-  schema: PropTypes.object,
-  readonly: PropTypes.bool
+  schema: PropTypes.object
 }
 
 export const widgets = { checkbox: CustomCheckboxWidget, time: CustomTimeWidget, text: CustomTextWidget }
diff --git a/src/utilities/schemaHandler.test.js b/src/utilities/schemaHandler.test.js
index 54434cd8..7646482a 100644
--- a/src/utilities/schemaHandler.test.js
+++ b/src/utilities/schemaHandler.test.js
@@ -157,12 +157,12 @@ test('Checks preProcessSchema modifies const schema to add missing default or ty
     { key: 'boolean_const', type: 'boolean' },
     { key: 'object_const', type: 'object' },
     { key: 'array_const', type: 'array' },
-    { key: 'null_const', type: 'null' }
+    { key: 'null_const', type: ['null', 'string'] }
   ]
   const processedSchema1 = preProcessSchema(testSchema1)
   expect(processedSchema1.properties.describedBy.default).toBe(testSchema1.properties.describedBy.const)
   for (const expectedType of expectedTypes) {
-    expect(processedSchema1.properties[expectedType.key].type).toBe(expectedType.type)
+    expect(processedSchema1.properties[expectedType.key].type).toStrictEqual(expectedType.type)
   }
 })
 
diff --git a/src/utilities/schemaHandlers.js b/src/utilities/schemaHandlers.js
index b1218f85..43bd7409 100644
--- a/src/utilities/schemaHandlers.js
+++ b/src/utilities/schemaHandlers.js
@@ -23,7 +23,11 @@ const preProcessHelper = (obj) => {
       // If default is undefined or not matching const value, set to const
       // Note: We use a custom text widget to autofill the const value and set the field as readonly.
       if (prop.const !== undefined) {
-        if (prop.type === undefined) { prop.type = guessType(prop.const) }
+        if (prop.type === undefined) {
+          const constType = guessType(prop.const)
+          // use nullable string type for null consts to enable allOf defaults
+          prop.type = constType === 'null' ? ['null', 'string'] : constType
+        }
         if (!deepEquals(prop.default, prop.const)) { prop.default = prop.const }
       }
 
diff --git a/src/utilities/uiUtils.js b/src/utilities/uiUtils.js
new file mode 100644
index 00000000..ad9fbf50
--- /dev/null
+++ b/src/utilities/uiUtils.js
@@ -0,0 +1,17 @@
+import React from 'react'
+
+/**
+ * Create an HTML link <a> element formatted as a button or a simple link. Link opens in a new tab.
+ * @param {string} url The link URL
+ * @param {string} text The text to display
+ * @param {string | null} tooltip The tooltip text
+ * @param {boolean | null} displayAsButton Flag to display the link as a button
+ * @returns HTML <a> element for formatted link
+ */
+export function getLinkAsButton (url, text, tooltip = '', displayAsButton = false) {
+  if (displayAsButton) {
+    return (<a href={url} target="_blank" rel='noreferrer' type="button" className="btn btn-default" title={tooltip}>{text}</a>)
+  } else {
+    return (<a href={url} target="_blank" rel='noreferrer' title={tooltip}>{text}</a>)
+  }
+}
diff --git a/src/utilities/uiUtils.test.js b/src/utilities/uiUtils.test.js
new file mode 100644
index 00000000..db6d3549
--- /dev/null
+++ b/src/utilities/uiUtils.test.js
@@ -0,0 +1,36 @@
+import { render, screen } from '@testing-library/react'
+import { getLinkAsButton } from './uiUtils'
+
+describe('uiUtils', () => {
+  describe('getLinkAsButton', () => {
+    const PLACEHOLDER_URL = 'https://example.com'
+    const PLACEHOLDER_TEXT = 'Example Link'
+    const PLACEHOLDER_TOOLTIP = 'This is an example link'
+    test('should return an <a> element with the correct attributes on default', () => {
+      const linkElement = getLinkAsButton(PLACEHOLDER_URL, PLACEHOLDER_TEXT)
+      render(linkElement)
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toBeInTheDocument()
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveAttribute('href', PLACEHOLDER_URL)
+      expect(screen.getByText(PLACEHOLDER_TEXT)).not.toHaveAttribute('title', PLACEHOLDER_TOOLTIP)
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveAttribute('target', '_blank')
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveAttribute('rel', 'noreferrer')
+      expect(screen.getByText(PLACEHOLDER_TEXT)).not.toHaveAttribute('type', 'button')
+      expect(screen.getByText(PLACEHOLDER_TEXT)).not.toHaveClass('btn')
+    })
+
+    test('should return an <a> element with a tooltip if specified', () => {
+      const linkElement = getLinkAsButton(PLACEHOLDER_URL, PLACEHOLDER_TEXT, PLACEHOLDER_TOOLTIP)
+      render(linkElement)
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toBeInTheDocument()
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveAttribute('title', PLACEHOLDER_TOOLTIP)
+    })
+
+    test('should return an <a> element with the correct button classes and type if displayAsButton is true', () => {
+      const linkElement = getLinkAsButton(PLACEHOLDER_URL, PLACEHOLDER_TEXT, PLACEHOLDER_TOOLTIP, true)
+      render(linkElement)
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toBeInTheDocument()
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveAttribute('type', 'button')
+      expect(screen.getByText(PLACEHOLDER_TEXT)).toHaveClass('btn btn-default')
+    })
+  })
+})