it will be adjusted when I merge latest staging

not required anymore, forgot to remove

I think a comment here is needed. Keep it and maybe mention rinseback alarm responses too.

Maybe this should be handled in OperationModes exec since it applies to all confirmations (not just alarm related ones).

There will be confirmations that are not handled here (e.g. power off). So we shouldn't fault in default - we should do nothing.

Shutdown would be handled somewhere else (buttons.c probably). It's not related to alarms.

Is this still possible since we're not returning to TxPaused from rinseback anymore?

Is rinseback completed an indication that we've done a blood prime following a temporary break?
If so, I guess this makes sense, but we have to do more than increase the UF volume. We have to adjust the UF rate so that we will reach the new (larger) UF volume when the treatment completes.
We also need to add RB volume to UF volume in pre-tx when treatment parameters are given/validated (for the final rinseback which we will always have so we should just plan for it before treatment starts).

What if multiple confirmations pending? Which ID will this function return?

Align comments.
Should substitution pump data be moved down to 0xBA instead of commented out?