Still haven't found another editor that lets you define a project with files from all over the filesystem rather than just from a folder. And no VS Code's multi-root projects do not cut it.
Sublime Text has a "Save Project As" option that will create a project with all the files that you have open, wherever they are located. When I tried to migrate to other programs that's one of the first things I try to do and they never have it.
Not exactly comparable since it's an IDE, but Eclipse had the concept of "linked resources" (files or folder that are part of the project but stored somewhere else on the file system) since at least twenty years.
Why not use symlinks (on Linux, not sure of the equivalent on Windows)?
New-Item -type SymbolicLink
Might actually be itemtype as argument thinking about it but get-help should tell you
tedious, error prone, tiring. NPP just works out of the box.