Mute block would be quite useful.
Setting up the Pearce BC-1 paths to work like my physical unit, so I can have AorB and A&B. Just bypassing the preamp leaves the raw signal flowing though. My work around has been to insert a Noise Gate block on both paths with the output turned all the way down, and merge those with the preamp bypass switch. When the preamp goes off, the gate comes on and "mutes" that path. When the preamp comes on, the NG is switched to bypass.
Still awaiting approval for access to IdeaScale.