Using the Soloist works fine unless you want to also have an actual Soloist. In that case just right click the bass track and change it to midi. Open notation, select bass and enter the notes you want. When done freeze the track. Freezing is important, if you don't Freeze Biab will generate a new bass part wiping out what you just did. Now with 2021 you have another option, use any track you want, change to midi, notate the part but now you can copy it to a Utility track. They don't regenerate so it's "frozen" automatically. Now you're free to change the bass RT part to something else.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.