With Shotcut you’re not importing, rather you are opening a file to be edited. All source media is left on your computer or storage devices connected to your computer.
If you have your camera on, plugged into your computer, then open a video file into Shotcut, it will write an absolute address (see Project Management) in the project file. The project file is just computer code.
Once you move/delete a source file, or if your camera shuts off, Shotcut doesn’t know where the file is at.
A better way of repairing a MLT file is to read Project Management. All instructions are posted there.
The ultimate way to avoid having to repair a MLT file is to have all files in the same folder where you save the project MLT file to. Don’t move/delete files in said folder that you use in your project. You can move the folder where ever, just not each file within that folder.
And to safeguard your work, do Save As, and add a date or a revision number in the file name. This gives you the ability do back up your work to a different file name.