Bookmarklets for adding margins

I love using my phone, but it's 2026 and for some blasted reason the phones don't even try to support extensions.

Bookmarklets still work. I would love to have bookmarklets to use for margin, from my phone.

My main use case is that I want to be able to select text and then get a somewhat filled out way to add a margin note. It would be nice if I could immediately make further edits to the note (replacing my existing annotation entirely).