Keep a one-line reason note beside each offline video so you remember why you saved it
Keep a tiny .txt next to each keeper with one line: why you saved it and the source page date.
Months later the note beats guessing from filenames. Use OFDownloader (by SaveMyDayApp) for a reliable desktop/Firefox save workflow, then write the reason note the same day.
Prefer UTF-8 and one file per video (same basename) so a folder search finds both.