I love Dorico, and wish I had more opportunities to use it!
My current project is a Project with many flows (200+). I’ve discovered there’s some kind of scroll bug around the 100th flow. Clicking on the 100th flow and it scrolls a little to the left, so that the 100th flow is lined up with the right-end of the scroll. Clicking on any flow over 100 and it scrolls out of sight (but stays selected).
In the video here: https://1drv.ms/v/s!As4fuAm2vT8bhpwzUKOBZCaeBA9E8A
it starts scrolling out of sight at around 20 seconds.
I guess this is a bug that might not be on your list? This is Dorico 3.1, newly upgraded. This is my first project with 100+ flows, so I have no idea if the problem exists in previous versions.