Shotcut does not manage media. This is a task for the user to do as they see fit.
The TL;DR is that Shotcut embeds relative paths in the .mlt project file if media is in the same folder as the .mlt file, or a subfolder. If the media is on a separate mount point or higher-level folder, an absolute path is used.
The ideal method is to copy all media into the .mlt file’s folder first, then bring the media into the Shotcut project so relative paths are used. Then the .mlt folder can be moved/copied to any other location (such as an archive) with no additional changes needed. The project should load fine from the archive location thanks to the relative paths in the .mlt file and localized media.
More info: