The "Grow on defeat" perk doesn't function.
One needs to load a new area or save (maybe, I haven't tried) in order for new bindable skills to show up in your toolbar after they are unlocked in the skill tree.
I haven't found a way to unbind a skill, in which case I feel there should be a method of doing so.
The skill "Give Up" keeps appearing in my toolbar every time I load a new level.