Excellent addon, I use with mpv (various settings like mpv.exe --ytdl-raw-options=format="bestvideo[height<=?1080]+bestaudio/best" to avoid 4K that my internet doesn't handle, mpv.exe --ytdl-raw-options=format=bestaudio for audio only),
to download videos with the help of youtube-dl and a bat file (can be done without a bat, I download both bestvideo and best),
to test pages on ESR (firefox.exe -profile "path\to\ESR\profile" -no-remote) or Chromium or Opera,
to use pre-Quantum addons like DownthemAll or HDS/HLS link detector on 56.0.2,
and more.
Very handy, highly recommended.

A suggestion:
Easy backup/restore entries option