As stated by rabidfox above, you can set a key bind on your keyboard to charge your rune arm, but there is also a feat under Artificer Class Feats labeled as "Rune Arm Use" that you can drag to your hotbar and use to toggle it on if that is your preference.No. You can put the rune arm auto-charge on the hotbar and toggle that on. But the fire itself can't be put on there; I personally rebound mine to the F key.
Sort of: you can map the Artificer Rune Arm Use feat to your hotbar, but this is a toggle, not a replacement fire button; when it's on, your Runearm will automatically recharge after every shot. You still need to press the "Use Rune Arm" button (default: left Alt) to fire.I would like to be able to fire my rune arm from the hotbar just like casting a spell or using any other ability.