This is actually applicable to any of the ARC-supported units (feel free to move to another sub-category):

RME ARC feature request for Main/Speaker-B Selection:

Is there any way to UNLINK the Main and Speaker-B volume controls from each other, but then have the ARC’s encoder swap to Speaker-B (volume control) when selecting the Speaker-B outputs?  Linking the two volume controls and swapping between them is not always a good idea in my unconventional setup - but I want to retain quick A/B toggling and volume control of them from the ARC.

I had a brainstorm that seems feasible:

If you can add a toggle action that will toggle the ARC’s encoder between Main Volume and Speaker-B Volume (similar to the existing toggle action between Main and Speaker-B outputs), then I can see a way to accomplish this with a single button with one more exception: If adding simple macro commands might be possible…

The required Macro (assigned to a single button):
Action1 = “Speaker-B Select” (toggle)
Action2 = “Encoder Volume = MAIN/Speaker-B” (toggle)

Hitting the assigned button will then toggle BOTH actions of selecting the Speaker-B outs and swapping the encoder to control Speaker-B’s Volume.

As long as TMFX boots-up in a known state, and the operator doesn't haphazardly engage one of the two settings (encoder control or main out actions) by itself to “break” the link between toggled states in the Macro, this *should* work reliably.

If RME is understandably hesitant about the possibility of the toggled states becoming unlinked, you could also use 2 separate buttons and 2 separate macros for this function (opposed to toggling with a single macro/single button):

You’d need to add an additional control category to the pull-down menus called “select” or similar (where you choose “toggle”, “push”, “encoder”).  This would “hard select” the chosen action opposed to toggling it – in this case “Main Out” and “Speaker-B” would be hard-selected in their respective Macros.  Then you would need to add a discrete “Main Out Select” action to the pull-down menu (already have the “Speaker-B Select” action), a "Speaker-B Volume" action, and you’re golden (as long as Macros might be possible ).

Main Out Macro:
Action1 = "Main Out Select" (select)
Action2 = "Main Volume" (encoder)

Speaker-B Macro:
Action1 = "Speaker-B Select" (select)
Action2 = "Speaker-B Volume" (encoder)

Probably not - but I figured my brainstorm was worth a post.  TMFX is really knocking my socks off as-is

Grazie