Do I really need to suggest this? I think I do. It’s coded into the game too but not fully implemented. I’ve changed the fullscreen=1 value in the user.xml file to fullscreen=0 just so that I could fix the horrible stuttering this game gives you in borderless fullscreen. I know I’ve heard from a friend that this was a fix for some errors in the previous iCBTs but I’m not sure which ones. Changing the values doesn’t work for everyone either so this is more like a broken temporary fix.
There’s even a reddit post on it here: https://www.reddit.com/r/treeofsavior/comments/3qhwtq/ways_to_increase_performance/cwff4tu
So IMC, please… PLEASE fully implement a true fullscreen mode. Borderless windowed fullscreen can reduce FPS by a huge amount and although it’s rather nice, it’s not very well optimized for the game.
And another thing. In this true fullscreen mode, I’m unable to ctrl-alt-delete or alt tab period. Just to get a near constant 60 FPS for ToS I have to go exit my game if I want to look something up or completely log off my profile on my PC if the servers go down in order to force quit the program. That’s not very fun if you ask me. I even considered changing the value back and to try to tolerate the constant screen stuttering and FPS drops that wasn’t there in iCBT2 but I feel that the FPS I’ve gained from full screen a necessity to play this game. 
So yeah, point in case is: As with a lot of other things this game needs, I feel that this feature is direly needed for the game’s overall performance and general happiness of the playerbase. At the very least a fix on the true fullscreen mode to enable it to allow alt-tabbing or showing task manager via ctrl-alt-delete would be highly desired.