You can do that with www.RapidComposer.com it will enter the chords from your midi keys as it plays, it's on special til 24th. It will run in VSTi mode in BB. You can then export and import to BB.
Sorry after years n years n years of wishing in the well and suggesting features that don't happen I just immediately look for workarounds. PG is in a bit of a time warp so you need to allow a 10-20 year difference.