Though parts of the UI are clumsy, such as even navigating to import flight plans, the main hair-pulling issue for me is the horrible contoller options system. Having to change to saved settings for aircraft by clicking left /right arrows, then waiting for the system to refresh, then going to the next, then the next, then the next is mind-boggling - and that’s with just a few aircraft! Down the road this access system will be a nightmare with even 10 aircraft, let alone 20-30!
This could be so much better with just drop downs! A drop-down menu would instantly show all saved aircraft, you slide the mouse down and click on it and done!