Since Gutenberg Saved Blocks is wreacking havoc all over the place, is it possible to build a Block Element and serve it using a shortcode? Trying to create 1 block (signup form) to be served in many places that is not easily hookable. ie. within page content.
I think you can accomplish something like this with GenerateBlocks Pro by adding a Local Template to the Template Library in which you add the Sign Up Form. (Here I assume you already use or built an asset that provides something like this for example Mailchimp for WordPress plugin or a block plugin that provides a sign up form like Genesis Blocks).
After you built the Local template Block, you can select it from the Generate Blocks Template Library Block (Tab Local Templates) on the pages where you want it to appear.
If you want the sign up form to appear on a huge amount of pages than the GeneratePress Premium Theme might be an interesting solution for you. In GeneratePress Premium you can create an element that you can hook into your content anywhere you like. Watch the video to see the concept how this works.
Hope this is what you mean.