Hi there @prakkarp! 
As you noted, there is no longer a built-in field to mark blocks as Required in the plugin-framework. This affects the terraform-plugin-doc tool as it defaults fields to optional if it can’t determine if it’s Required.
Currently, there are 3 validators that will help you achieve the same functionality as a required block that can be used with ListNestedBlock , SetNestedBlock , or SingleNestedBlock respectively.
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listvalidator.IsRequired→ListNestedBlock -
objectvalidator.IsRequired→SetNestedBlock -
setvalidator.IsRequired→SingleNestedBlock
As for the documentation, currently you’ll have to workaround the documentation generation tool to avoid it being shown as optional by using a manual template.
You can run an initial generation to get your fields/descriptions, then insert them into a template. Here is an example from our cloudinit provider:
Available fields for use in your templates are documented here