Sorry, my mistake.
In Set List Maker there is no way to hide recordings that other bandmates added. If the recording is faded in the Recordings list, that means it's not attached to any songs. If the recordings are local, you can delete them if they are no longer needed. If they are linked from iTunes, they will appear in the list if they are linked to a song or they have had some metadata like volume or trim saved for them, and you can't remove them from the list if either of those conditions is true.