Can modular pages have a custom blueprint?

I have a modular template named 'cta_block.html.twig' and a blueprint named 'cat_block.yaml' that defines custom fields for creating call-to-action blocks. I can see and assign the 'Cta block' template to the modular page when creating it, but after I assign the template and save the modular page I don't see the custom form fields that I defined in the blueprint.

I resolved this. Blueprints for modular subpages have to go in the blueprints/modular folder. I had mine in the blueprints folder. It's obvious now that I think about it.