I don’t know anything about Bitwig.
You should be able to use Scaler to eg. set up a Bass line you like. Take the midi (drag 'n drop) onto a midi track. Go into the midi editor, select all and change the selection to a different midi channel and assign your instrument.
In some DAWs you can just re-route midi channels. Sometimes you can even mix DAWs using reWire.
Hopefully someone will chime in with a better answer.
I feel your pain.