I may be misunderstanding the concept of flows, but is it envisioned that you will be able to import flows from one project to another? I can’t see how you can do it at the moment, but I can imagine in order to keep a project from consuming all your computer processing, that sizable flows are created in separate projects, and then assembled in a separate master project where the full score is finally tweaked ready for printing, or for ultimately exporting a final comp audio track.

You will be able to import into flows in the future. Hopefully, Dorico will be efficient enough that you can run an entire score in one file.