Allow block attributes/functionality in a template to be locked/removed

[pbearne]

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When creating a template via PHP CPT (or other methods) I Would like to be able to set default content eg. text/values for attributes
And
to be able to control options by setting defaults and removing options
eg.
be able to set the heading level in core/heading
be able to remove the ability to set h1 in core/heading

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I would like to part of the template array

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This might be posable via JS but would need a way to target a CPT template set
or we could create a complete set of custom blocks but this requires duplicate code (not DRY) and ongoing maintenance

If I am creating a complex page layout with several headers and paragraphs I would to be-able set h2 for the fist and h3 for rest all from the create CPT PHP function

[talldan]

@pbearne, you can already set values for attributes when creating a template. You can see in the documentation below, the example sets an align value for the image block and a placeholder value for the heading block:
https://developer.wordpress.org/block-editor/developers/block-api/block-templates/#custom-post-types

Any attribute can be set this way. The hardest part is knowing what the attribute is called for each block. At the moment there's no documentation (#6190). The easiest way is to browse the codebase and look at the block.json for each block:
https://github.com/WordPress/gutenberg/tree/master/packages/block-library/src

Within the block.json file there's a list of the attributes that can be changes and the type of the attribute. So for heading you can see level is a number:
https://github.com/WordPress/gutenberg/blob/master/packages/block-library/src/heading/block.json

In terms of locking/removing attributes, that's an interesting suggestion. It ties in a bit with what's suggested on this issue - #7931, though that's more at the editor level.

I've taken the liberty of updating the issue title, given that part of your suggestion was already possible.