So once you right click on your root note and select Scale you will get the midi in your track that you need to add a midi synth to that track or go to File > Export Project Midi
and just open in Realband.


Here's some templates that might help.
This is just a UserTrack Template in C after you make the midi in Reaper you can bring it back to Realband Drag it out as wav from the drop station then drag it back into Realband then save as an SGU and select the wav track as your Audio track and that will give you a UT in C, save the RB UT C as an SEQ, now delete the wav track and now you can Transpose the Key then do the same again saving it in the next key.
You will then have a UT.
Song_30m_Pop_1_C_PopChords_Markers.zip