Navigation block's responsive modal can't be customized

[iandunn]

What problem does this address?

I'd like to be able to implement a design like the following, where the responsive menu doesn't take over the entire screen, and contains more than just links:

That doesn't seem possible right now, unless I resort to an ugly hack like filtering render_block.

For now I've turned off Enable responsive menu, and am building the open/close functionality myself. That's not too awful, but it'd be ideal if the contents could be customized without having to do that.

What is your proposed solution?

Maybe support a block-template-parts/responsive-navigation.html template?

I'm open to other ideas as well.

[getdave]

Closing in favour of #38201 where there is more discussion on the same topic.