Layout: Collapsible/Moveable containers for modular sites

In it’s simplest terms:
I’d love to see a simple collapsible container/wrapper for visually grouping form fields (see quick mockup attached), with options for it to be closed by default. Long web pages with lots of form fields result in very cluttered and visually overwhelming panels.

More advanced:
Ideally it would extend into a NON-WYSIWYG modular way to represent our web pages in the panel (using snippets). With option to order the collapsible field containers - without using subpages, clicking to open a panel or clicking through to another page.

The blocks field is great for users wanting a ‘site builder’ backend but often users just want a simple ‘site editor’ style backend, mainly using fields and structured data. The kirby-fields-block plugin pretty much achieves the above but it doesn’t support columns, option to add new blocks can’t be deactivated easily etc - guessing it’s just not quite what the plugin is intended for.

Kirby 4 has brought field preview natively to blocks