Smarter share sheet to avoid breaking triggers

There are existing Canny requests with ideas about making more of the share sheet extension.
But I'm coming at it here from the plugin perspective, as another knock-on from the introduction of triggers, which necessitate more use of frontmatter, even in daily notes. (#411 is another recent example.)

Currently: the only option from the share sheet extension is to prepend text to a daily note.
Issue: this then stops frontmatter from being frontmatter, stopping triggers from working. Hence this is now closer to a Bug than a Feature Request.

Ideal solution: be smarter at where to insert the text. For nearly 2 years now my plugins, calculate a smart insertion point that comes after any H1 title and initial preamble, and now after any frontmatter too. If you want to see the logic, it's in helpers/paragraph.js::calcSmartPrependPoint.