В процессе изучения

This is a problem every mmorpg skill based has.

Personally i don't think this is really needed. I use a key to open the Action Progression window when i'm leveling and it's pretty fast to switch it on-off.

Maybe a more compacted window with all the progress shown (only the actual uncompleted levels), without the need to click on the skill levels to branch out, could be of some use.