There are probalby a number of mods out there that do this, possibly a way to script one in Discord (don't know enough to make scripts for this myself).
CT_BarMod puts in a simple options wher eyou choose SHIFT, ALT or CTRL as a hold down key to self cast when you mouse click a spell, however that same mod also causes artifact buff icons in the old party frame space.
Good feature for DAB, have self cast where you can choose those keys (or others) as the self cast trigger.