Yes, I’ve been using WL for 20 years… however… I have never used multiple montages at once… or ‘file groups’. I fully stipulate that this is probably an RTFM.
I want to be able to have a Montage (as I always do) that routes through the master processing and then…
Open other files at the same time I can use as a reference track which does -not- go through the master processing.
And then toggle back and forth between the Montage and the reference tracks.
Can do? How?
In Montage create a Reference track the purpose is just that a Reference…
Read up on Reference Track in the pdf manual or online…
https://steinberg.help/wavelab_pro/v11/en/search.html?searchQuery=reference+track+routing
regards S-EH
Oooooooooooooh. 
And… very elegantly implemented, I must say. The toughest part was learning of its existence… and then figuring out how to add it.
THANKS!
S-EHansson is right. But is it also possible to display two montages at the same time, and to toggle playback from one another, by clicking on the time rulers. But A/B is better with the reference track.