The Table of Content extension seems to work well in threads 🙂
Too bad I have like 100 indexed blog posts that I wish it worked for.
Not to keen on converting posts into threads..
Edit: Perhaps I spoke too soon.
I pasted one of my blog posts as a thread and the font size went bananas. Starting at 14px, ending at 4px by the end.
Don't know if it's my bad formating, or if it has to do with that extension.
Will try some more when I've put the kids to sleep. 🥱