I am assuming that you are making a distinction between video files and project files.
Assuming video files....never move, delete, or rename files/folders that went into a project after the project is saved closed.
When you import media into a project, all you have in the project are copies of the originals. The originals are still on the hard drive. But, the project
needs to trace back to those originals at their hard drive save location. So, determine to what active project the videos are
You can look into the concept of project archiving. In this approach a copy of the project file and copies of its sources media are
saved to the computer hard drive in its own folder. Consequently, originals of the source media at their hard drive save location can be deleted because the copies of the project file and source media are isolated in the archives folder.
But, to me, that has the ring of a trade off rather than a direct deletion.
Please review and consider and then we can discuss this further. Please provide more information if I am not targeting what you seek.