Currently, the SD recording is primarily intended as a way to simply capture multi-track recordings of live performances without the need for a computer.
Lacking things like markers (both creating and navigating), better navigation of long recordings (the jog function is limited), recording to existing sessions, creating sessions from Capture or S1 to import to SD card, etc., it's not going to be a complete replacement for recording and playback and editing like you would with a DAW like Studio One or even Capture.
There's also the Virtual Sound Check capabilities, but they're subject to the same limitations as far as markers, navigation, and session creation. It's easy to multi-track record a single song played live by the band, or even a couple of songs, to SD to use as your Virtual Sound Check session, but it's not easy to take a two hour set and try to do Virtual Sound Check with the song at 1h:15 into the recording, or to create a session with just the song or two you want to use for this outside of the SD Recorder on the mixer, like in S1 or Capture.
You can certainly play backing tracks from an SD recording as backing tracks live, but you'll probably find that its not well suited to it, as there's also no good way to edit or manipulate an SD session outside of the mixer, so trying to organize backing tracks for SD card playback would be a real challenge, if possible at all. You also don't have an easy way to move around a long session, or see which channels have tracks recorded, etc.
It's just not designed to do this currently. It might be a feature or capability that could be implemented in the future though.
