Pretty sure this is a major bug

Daniel, no apology is necessary. This first project is a learning experience for me, and I expected to do a bit of stumbling around. Even so, I’m certain that the advice you gave me was still the right approach for this project, and it plays to Dorico’s strengths. I’d be happy to send you my project when I get home tonight.

Might you and your team consider rethinking what happens when you detach a flow from a layout?
The notes are also there, lurking and orphaned, but they are not deleted. Certain engraving changes (Frame, System, and Note Spacing markers, etc) are not deleted. Lyric and note head positions are retained. At present the logic does not seem to be applied consistently. In my estimation, deleting certain layout and frame edits doesn’t provide a benefit to the user. Instead, it seems to unnecessarily hobble the use of frames. Perhaps my project is a bit unique. Even so, I think it’s an attempt to use Dorico as Dorico is intended to be used. The concept of flows may be the single greatest innovation that Dorico brings to the world of notation software. Why make this concept less powerful?

I split my project of 350 flows into 4 separate projects - each containing no more than 100 flows (100 being the soft max based on the scroll bar weirdness). When all 100 flows are active, my system starts being a bit sluggish. I had hoped to work on 25 flows at a time. This worked fine until I came back to the first set of 25 and realized that most, but not all, of my engraving edits had disappeared. In the future, I’ll start with 25 at a time but leave each set active until I get to 100. If this proves too cumbersome, I’ll split my project into sets of 50. The only problem with that approach is that is becomes more difficult to maintain uniform layout and notation settings across multiple projects. Regardless, I’m still loving Dorico!