I think I’m experiencing a bug where chord symbol regions are not shortened or split when deleting bars either via the system track or the Shift+B popover. I discovered this when I had deleted about 40 bars at the end of the flow, which had a bass part with a chord symbol region that extended to the final bar.
I later went to export the parts and discovered each part had 40 bars of rests, and when I went back to look at the flow the chord symbol region had forced the bars to reappear as it was still the same length. I had to then manually shorten the chord symbol region using the handle.
Obviously it would also be helpful to be able to use the scissor tool to split a chord symbol region as you can do with a slash region.