in orders.lua:
Arty = "{categories.ARTILLERY}",
so I think there must something like:
Arty = "{categories.ARTILLERY * categories.MOBILE * T2MobileMissiles * T3MobileMissile}",
I'm not a programmer, but that's what it's supposed to look like.
So I hope you will help)

Hi!
How to add Mobile Missile Launcher in list ? I want give an order my arty shoot in T2, T3 rocket units, when they will be in range.
It would be ideal to add t2/t3 Mobile Missile Launchers to the "arty" button
https://forums.faforever.com/viewtopic.php?f=41&t=17047