If you are restricted with the 255 SGU bar limit you can do it with the Biab Plugin by highlight the existing chord regions in Reaper then "Insert Bars" then "Biab Plugin Chords".
You can also use RealBand as it will also let you create lots of different endings and sections.
You can then save the chords as musicXML then drag n drop into Reaper and use the "MusicXML Chords" button.

In the pic I'm using the fill colors but at the moment it don't use the fills so say no to fill colors. I'm working on the fills at the moment so it will play them automatically or when you hit the same chord.

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Biab Track Injector for Reaper
Free Biab Chord Picker Tool