You could probably do that with KV Element
within Biab or sending to a DAW and returning back to Biab.
You should be able to send tracks with ReaStreamVST to say the Audio track that has KV Element with an FX chain.
In the guitar tracks put reastream-standalone.dll and Sonalksis FreeG after it to mute the output to master.
In the Audio track I load KV_Element.dll then in that I load reastream-standalone.dll using Guitar 1 for ID
after it I Sonalksis FreeG connect to audio out to give level control.
You can put it in the Master (Combo) but you need to connect audio in to audio out.
Sonalksis FreeG Stereo (64 bit).dll
Sonalksis FreeG Mono (64 bit).dll
EDIT: here's a mixer 12 channel mixer vst with 5 sends Win/Machttps://audiostrom.com/?topic=mixer
EDIT: here's another pic send 1 guitar to Amplitube then to master.