I did this with an elite controller but I imagine you can do it with any controller that has paddles. Since weapon action takes up a Photon Art spot on your weapon, I was trying to figure out how to get around it.
In-game, I mapped the "Select" button to weapon action. This, of course, removes your ability to access the quick menu (more on that later). After that, you can map "Select" to a back paddle on your controller. Now you can use the weapon action while freeing up space for an additional photon art.
You can map buttons for when in OTS mode. You can re-map the quick menu to "select" there. So whenever you want to access the quick menu, you zoom in and press select. A minor hindrance to be able to free up a spot for another photon art IMO.