Is it possible to link a unit to a dialog item?
I'd like to be able to make the players cast abilities on their allies by pressing quick-access buttons.
I want the players to be able to select the ability is literally cast it on the button, while it redirects the effects on the hero. Is this possible?

If not, I guess it is possible to just set one 'Heal' button for each Hero and let the Medic player click those to heal them?

Yea its possible. Depends on the scale of it though.

Are we talking about heroes healing heroes or an army?

Well, I'm trying to establish how the Custom UI will look like and how players would interact with it.
It's for the Infiltration RPG project.

So, at most 4 players to interact with.
I was at first thinking I could make all players target some specific spells on any hero with a Quick-Access button, but then I found it to be a horrible idea... BUT, letting the Medic (a probe), use those Quick-Access buttons to heal his partners might be useful (though this is still to be proven).

P.S. If any of you have ideas for the Custom UI, please go on... I already sense the fail of the design I have in mind.

EDIT: By the way, the main question behind this thread is simply to know if you can detect if a player has pressed a specific ability's button without casting it, just leaving it to the cast-cursor.

Button pressed event detects command card button presses.

So you have something like

Button Pressed -> Set var to true
Dialog item is pressed -> var is true -> order unit -> set var false
Unit uses ability -> set var false