In a nutshell, the above is creating Multiriffs in Biab the same way that they are created in RealBand.
This way was pointed out to show Win uses that don't or can't use RealBand or Mac users that don't have RealBand, how to create MultiRiffs.

All the tracks are save to a stereo track except the realtrack instrument you want to create 7 Multiriffs to choose from.
That saved stereo track is then loaded into the Audio track of the song, then the same RealTrack is loaded in each of the 7 Biab tracks,
F5 is used on each track to generate the instrument only from bar 8 to 12, this works the same as RealBand generating a MulltiRiff for the selected bars.

Now you solo the audio track and solo the first track,
you play this and see how it sounds, if it fits good then highlight bars 8 to 12 and drag export it into bar 8 of your DAW, or don't highlight and drag export the whole track to your DAW,
else solo track 2 and play as it might play a better Riff or track 3 or 4 or 5 or 6 or lucky 7. If you still can't find a suitable riff then just hit the regenerate all.

As mentioned above, if PG would automate the muting of all bars that are not highlighted (except Audio slot without having to F5 mute track , un-mute track), and then generate up 7 of the same RTs.
(this should be quick to generate up as the other bars are muted, actually empty),
This could be done with one button "MultiRiff" as you click the button it will bring the RealTrack picker window up, you select the RT > OK > Biab will then generate up the 7 tracks to the whole chord sheet or just the selected bars if selected.

Biab Track Injector for Reaper
Free Biab Chord Picker Tool