Great product and new features! Will definitely try it out when I get a chance. While I am right in your target user base, over a decade ago I built https://zetabee.com/text for myself and even though there are now so many better solutions to the text outlining problem, it is just too difficult for me to switch. Not sure what your keyboard binding for collapse/expand is but I played with backtick (single key) and loved it because it just feels natural and I never type ` in my notes.

Long ago, I tried to make a better autocomplete feature so people with speech disabilities have fewer buttons to push. Here's what I did - https://ktype.net/wiki/research:articles:progress_20110209 - basically broke down tweets into n-grams (1-4) and then used the 5 most likely next words as suggestions. If I were to do this today, I would still try to get a large volume of text in my target use case (what do most of your users type? Tech project notes? home construction items? grocery lists) and break them down into large lists of 2-3 n-grams. Then ask GPT3 (or equivalent) for 3 possible suggestion for next 1-2 words and save them. Compress and hard-code this list into the app (or alternatively make it download/update from your site infrequently).

If you would like me to explain more, please feel free to reach out!