How to mark a print as complete?

There are some prints I had to reupload but I want to mark them as completed because I use it to kinda see the progress of multi-part prints.

I don't mind digging in a json or database, I just don't know where should I look for this metadata and what should I set it to mark it as printed.

Take a look at the file in /home/pi/.octoprint/uploads/.metadata.json and compare completed files with non-completed files.

There will be a .metadata.json file for each sub-folder as well...