I actually thought this was previously possible, so it may be a bug or I may have imagined it!
If an effect is running, and you tap [Effect] to open it in the CIA I thought it was possible to tap the channel list and then the {Offset} SK to change the offset. i.e. if the channel list is 210 > 239 you could tap that, then {Offset}, then {Mirror Out} to re-build that channel list in the mirrored-out order.
This doesn't work, you need to tap the channel list then manually enter 210 [Thru] 239 {Offset} {Mirror Out}