Unborn Lich Ravenous Staff auto-fills other button slots

So I want to have my two spells (Feast of Flesh) on "Shift + E" (and His Foul Emergence) on "Shift +R".

But because I have a free "T" slot, HFE gets autoassigned to "T" and it's messing with my rotation.

I can't seem to keep whatever I assign to the buttons I assign.

Same.