Hi!
Here is two annotation improvements that I believe is very important.

1. Annotation window should be in the Sumatra PDF, not a floating window. It can be on the right by default, just like a bookmark window. Floating annotation window does not make sense at all in terms of user experience.
2. As mentioned in Set annotation color defaults #1734, setting default annotation style is not possible. Example: I use yellow (same as default), but I use more transparent highlighting. In every highlight, I need to change the opacity manually. The usual way: The PDF reader remembers the last annotation style and uses that until further changes.