Load form if it's defined in another document?

This relates to form registration, so maybe there's a different solution.

At the moment the form needs to be loaded in the store to render correctly, e.g. with the form defined in the local document or in another document that was visited previously in the same mashlib session.

I want to instead define which form should be used in the local document or in my preferences file.
I would then need the form pane to load the document defining the form before trying to render it, e.g. loading not/yet/loaded prior to rendering the form.

<#Class> ui:annotationForm <not/yet/loaded#MyForm> .

It appears the easiest option would be to wrap the appendForm with kb.fetcher.nowOrWhenFetched here:

https://github.com/solid/solid-panes/blob/f9aeaef823bbf98714208cdce56371653618e0be/src/form/pane.js#L123-L133

However this would also introduce an async behaviour where there is none at the moment.

Start in src/form/pane.js at appendForm around lines 123-133, then trace how form registration and the local store are used before rendering. Compare the proposed kb.fetcher.nowOrWhenFetched flow with the current synchronous behavior; done means a form defined in another document can be declared locally or in preferences, loaded, and rendered without breaking existing forms.