Annotations is a cool feature indeed.

It might be cool to make YouTube user's names/channel links/video
links clickable (rather with the possibility of opening them in tabs).
Because lots of people link to others in their videos.

I have been experiencing difficulties with the disappearing notes as
well. Which makes it really hard to time everything. I would to make
subtitles with annotations, but this little disappearing makes it
practically impossible.

Could there be a timeline on the bottom of the video you can drag your
notes in (so for the bigger the box is dragged, the longer it is
displayed)? And in which you can drag the ends of the notes to make
them start earlier/end later etc.?