Wait…
What about Project Panels?
https://npp-user-manual.org/docs/session/#project-panels
The Project Panels are similar to the Folder as Workspace panel, but allow you to organize the tree view to your liking, rather than being forced to follow the Windows filesystem hiearchy.
Double-clicking on a file from the tree-view will open it as a new tab in the Notepad++ editor (or will activate that tab if it’s already open). Closing the tab for a file from the Project will not remove it from the Project panel, so it’s easy to re-open that file.
I have a list of often used files sorted by folders (according to my needs, not by Windows filesystem hierarchy) and it works fine for me. And works fine with spaces in file names.