It sounds like you are using the playlist as a “bin” to keep your project media. I think this is OK in simple cases, but fundamentally, the playlist is for playing clips in a certain order and that is what the functionality is focused on. I do not want to add features to the playlist that confuse it’s purpose. Maybe someday someone will add a more advanced project management and binning feature with folders, searching and other features people would expect.
In the meantime, I recommend to create a folder for each project and keep the media for each project in its respective folder.
There is some good context here if you have not see this: Project Management