OK. I put my documents/ notes/ writing in one file. Headings preserve structure. The core outline plugin allows the headers to be moved around.
I also convert to OPML allowing import into Workflowy and mindmappers. Workflowy gives outline and kanban views, with easy rearrangement by mouse or keyboard. Mindmappers ditto according to the program, but I use them less often. Export back via OPML takes less than a minute.