[Lens] [Docs] Add more QA for Lens

docs/user/dashboard/lens.asciidoc

@@ -156,11 +156,15 @@ A subset of *Lens* visualizations support value labels.
 [role="screenshot"]
 image::images/lens_value_labels_xychart_toggle.png[Lens Bar chart value labels menu]
 
+Note: it is not possible yet to control the labels position in bar visualizations.
+
 * *Pie*, *Donut*, and *Treemap*
 +
 [role="screenshot"]
 image::images/lens_value_labels_partition_toggle.png[Lens Pie chart value labels menu]
 
+Other type of visualizations do not support labels yet.
+
 [float]
 [[what-is-the-other-category]]
 ===== What data is categorized as Other?
@@ -207,7 +211,10 @@ refer to <<explore-fields-in-your-data,Explore the fields in your data>>.
 [[is-it-possible-to-sort-dimensions-in-a-chart]]
 ===== How do I sort the dimensions in a chart?
 
-Sorting dimensions in visualizations is unsupported in *Lens*.
+Sorting dimensions in visualizations is unsupported in *Lens* for charts.
+
+Sorting is possible in *Lens* datatables, but it is limited to a single column. Click on the dimension header to sort by the dimension/column and select the sorting criteria.
+Note that if the dimension is used within the `Columns` (transposed) then all columns that belong to the same dimension will be sorted.
 
 [float]
 [[is-it-possible-to-use-saved-serches-in-lens]]
@@ -220,3 +227,43 @@ Visualizing saved searches in unsupported in *Lens*.
 ===== How do I change the number of suggestions?
 
 Configuring the *Suggestions* that *Lens* automatically populates is unsupported.
+
+[float]
+[[is-it-possible-to-use-different-indexpatterns-in-lens]]
+===== Is it possible to use different index patterns in a single visualization?
+
+You can create a visualization from multiple index patterns in *Lens*: this feature is available for a subset of visualizations such *Bar*, *Line* and *Area* charts.
+
+Each *Layer* in a visualization is associated with an index pattern and mutiple *Layers* can be combined together within the same visualization. Each *Layer* also has a chart switcher button in order to select the best type of visualization for the specific dataset.
+At the same time it is possible to dynamically change the indexpattern for the *Layer* when required.
+
+[float]
+[[why-my-field-x-is-missing-from-the-fields-list]]
+===== Why is my field X missing from the fields list in Lens?
+
+*Lens* does not support the visualization of full-text fields, therefore it is not showing them in the data summary.
+You will still see the `X.keyword` field, when available.
+
+[float]
+[[how-to-handle-gaps-in-time-series-visualizations]]
+===== How to handle gaps in time series visualizations?
+
+*Lens* provides a set of features to handle missing values for *Area* and *Line* visualization.
+This is useful for sparse data in time series.
+
+To select a different way to represent missing values, click on the *brush* button above the visualization in the editor to see a selection of strategies to handle missing values. The default strategy is to hide the gaps.
+
+[float]
+[[is-it-possible-to-change-the-scale-of-Y-axis]]
+===== Is it possible to change the scale of the Y axis in a visualization?
+
+At the moment it is not possible to change the scale of the Y axis (for instance, making it start from another value than 0) in *Lens*.
+
+[float]
+[[is-it-possible-to-have-more-than-one-Y-axis-scale]]
+===== Is it possible to have more than one Y axis scale in visualization?
+
+*Lens* lets you pick, for each Y dimension, up to two distinct axis: *left* and *right*. Each axis can have a different scale.
+
+
+