Ability to play an "unmatched file"

[FelixSchwarz]

I wanted to use dim to share family videos + other private recordings which are obviously neither a known movie nor a show. It seems to me as if each media item in dim must be "matched".
Is there a way of just importing some private videos? Can I somehow add the metadata in a custom file?

This seems to be a pretty basic question but I did not find any docs regarding that so far.