atm one cannot drop vials .. you have to use it / throw it to get rid of it .. which is annoying and can be deadly in some cases (mecha knights)
i'd suggest to make them droppable or make one able to delete them (x-them out) or make them poof if they're unwanted
Otherwise you wouldn't be asking that question. You used to be able to drop them.
^^ What Autofire said.
I'd rather we be able to throw three vials at once, preferably with some flashy explosive effects, perhaps by using the modifier key in combination with the vial slot key, or by holding the vial slot key down. If it's a Mecha Knight, just summon all the ones you currently have in that slot simultaneously
"You are experiencing a PICNIC ERROR!
Dropping was removed for an exploit. However, getting rid of them altogether is an option..."