You could put all of your different buttons into a family and assign an instance variable to the family, where you store the desired action.
Then you check for mouseclicks like so:
On left mouse button clicked on ButtonFamily -> call function CheckForButtonPress(ButtonFamily.UID)
On Function "CheckForButtonPress"
Pick ButtonFamily with UID function.param 0
ButtonFamily.Variable = "menu" -> Call Menu
ButtonFamily.Variable="quit" -> Quit
I hope it's somewhat understandable.
But it will not work with the free version of Construct 2, because of families.