Lugi,
Sorry I didn't see this post till now. I hope you've figure it out, but if not here is what you do. Make sure you are using software 2.01 or higher. Then, after you record your backing sequence, just hit the song sequencer button and the tracks for the song in the backing sequencer will show up as numbers in the tracks you've recorded. The tracks with no numbers (blank) can be recorded. This is how you add additional tracks to a backing sequence song. Then, just save the song and your done.
George Kaye
Kaye's Music Scene
Reseda, California
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George Kaye
Kaye's Music Scene (Closed after 51 years)
West Hills, California
(Retired 2021)