When I import a flow into a project, I noticed, that I loose a lot of information from my original flow, like the properties for accidental visability, manual bracketing and barline changes, notation options and much more.
I hope for more options for importing flows in the future. It’s a lot of extra work, when I put a publication together from a lot of single files to check everything and to repeat the settings I have already done.
I am running in the same problem. By importing flows with different custom notehead sets these sets are no more available in the project. In this case the import function is nearly useless.
Try saving the Notehead Sets as default (from the source project(s)) in order that they’ll be made available in the destination project(s). Then try importing the flow(s).