Do you have a picture of what this should look like? You cannot upload here, but you can put the picture on a sharing site and link to it.

More on hanging indents here:

I don’t have a lot of experience with adding accessibility to interactive buttons, but I know who does… and they’re going to be speaking at The InDesign + A11Y Summit next month:

The InDesign + Accessibility Summit:A CreativePro Online Event

:-)

Which version of InDesign are you using? They added the on-character and on-frame opentype menus a couple years ago:
https://idsecrets.wpengine.com/fast-way-apply-opentype-features-text.php

Oh… hm… I cannot think of any way to do that with InDesign. One numbering level cannot refer to some other section or list, other than an earlier Level. Might be possible with a custom script, if you had to do this often.