to the best of my knowledge (which is far from considerable! <img src="/ubbthreads/images/graemlins/stupid.gif" alt="" />), it can't be done.
it IS possible to assign potions to most letter and number keys, however why you'd wish to do this i can't imagine. i suppose if you use a lot of mana potions and your mage is your lead character it might make sense.
to truly make 'quick-key' potions advantageous, there would have to be a way to make the potion available to either/both characters simultaneously. there's not. they're available to the character designated as leader, meaning it takes three keystrokes to provide a potion to each/both and at that point you're better off simply pausing the game.
should you wish to proceed anyway, here is how. hover your cursor over a potion. press an 'F' key (F6 for example). quit the game. open your BD directory (example: C:\Program Files\Larian Studios\Beyond Divinity) and look for 'keylist.txt'. this should open in notepad. scroll to the very bottom of the page and look for this area -
"# Floating icon keys : ***************** "
under this heading you'll find your assigned 'F' keys (example - "8137 - f6 -").
change the 'f6' part to 'm' (for example). save (under 'file') and exit.
pressing the 'm' key will now drink a health potion for the leader (8137 being a numerical designation for the health potion).
when designating a letter, make sure to use lower case letters (m) even though it will save and read as a capital 'M' later.
all of my experimenting with the numpad and combining a 'switch (changing leader) and drink' into a single keystroke were unsuccessful.
