Great Weapon Master (GWM): Please please stick to the 5e rules and make it optional to use. GWM's efficiency is always dependent on the characters to-hit modifier and the enemies AC. Especially in early levels a forced -5 on hit is really hurting
You can already toggle GWM effect on/off in the reactions box. The UI will certainly be improved at some point, there's been several other elusive UI elements that I've found by accident or read from forums.
Oh thanks for the hint. Kinda strange to put it into the reaction box. Did you by any chance find out where Feats of characters are displayed in the character sheet?