>>> And can someone explain why anyone would want to use it? Maybe I'm just being an old grump, but I become unreasonably irritable when I see those grey blanks appear.

The analogy would be to read a full page of text, that had no paragraph breaks in it. Much easier to read with paragraph breaks. Reading a page of chords without line breaks is similar. I think the idea of sections starting on a new line make the structure of the song more apparent.

For example, I saw a song with a 1 bar introduction, followed by the typical AABA 32 bar form. Without section breaks, every one of the new part markers starts in the middle of a line, and the form isn't apparent. With a single section break, the 32 bar form (4 x 8 bar sections) is apparent.

The feature has some rules about when it "won't" break a line, in general, when the new line would be small (1 or 2 bars), then it won't break for a new line.
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>> Bar 45 is missing and there are lots of instances where I would expect new lines.

Regarding the posted screenshot, the expected new lines won't happen because they'd create a small line (as discussed above), so the feature is working as designed there. The song looks to have a tag in it, I would need to know what tag settings are used - not sure why bar 46 isn't shown, perhaps it is some combination of a song with a tag and a certain placement of part markers.

If a single song doesn't look better with the section breaks, I wouldn't turn them off completely, because they make most songs look good. You can turn them off for a single song (Edit - settings for this song)

Have Fun!
Peter Gannon
PG Music Inc.