I would love to help fund a program lets users a) create "collections" of files which are accessed by a tree-view panel on the left side of the screen, and b) associate metadata with those files by creating and populating user-definable columns of data in the main window.
For example, you could create a collection called "movies" and tell the app to look in two different folders on your computer for files to add to that collection. Once the files are in the collection, they show up in the main window in a view that mirrors Explorer's "details" view. From here, users can right-click the column header and choose "add column". You could add one called "release year" or one called "genre" or one called "director". You could then populate these fields in-line, and the program would associate that data with the appropriate file, storing everything in XML files or some other database. These custom columns would be specific to each collection, so if I chose a collection called "comics" from the tree panel on the left, I would see different custom columns than if I chose "research papers". The columns would all be sortable, and double-clicking a file would open it with the system-defined software.
That's all there is to the interface - a nested tree-view on the left where collections can be sorted into folders, and a file view in the main window with definable columns of data. A simple toolbar or menu could let you add/remove collections, choose folders, add files, etc.
As for similar software, there's stuff out there, but it all specializes in specific kinds of files. Foobar lets you do this for music, and there are apps that do it for comics, for videos, for ebooks, for retro video game roms, and so forth. But they're all specialist programs that also bring in data scrapers and file launchers and cover art and all the rest. This program would forgo all of that in favor of simplicity and flexibility.
I don't know what it would take to create such a thing, but if anyone is interested in giving it a shot, I would be happy to throw some $$ at it. It's something that, if done right, I can imagine myself using on a daily basis.
Thanks for reading!