2 stars only because this still has the same problem that was mentioned in these reviews 4 years ago. I see that this addon has been updated since then without fixing this fault. As previously mentioned, the first timestamp is added correctly, but subsequent timestamps get added without deleting the first timestamp which takes priority, rendering subsequent timestamps useless.

thank you but I do not understand why most you youtube bookmark creators, don't realize there might be need to create more than one timestamp for one video.

same as "YouTube Parts Looper & Bookmarker" ; "YouTube Timestamp Bookmarker" ; "YouTube Browser Bookmark Tagger" they all give you only one shot, after which you have to go into the library and rename the bookmark in order to make a new timestamp through the addon button.
defeats the purpose.

I might as well use ctrl-D and write the time myself into the title at that point.

great idea; poor execution. at least make it optional through a toggle in options.

Nice addon but it's stopped working. As of 2021-04-02, it has this problem:

When the first bookmark is made, it correctly adds the timestamp to end of the URL like so:

...&feature=youtu.be&t=21

If the video is then started with that bookmark, and the bookmark is later updated then *both* timestamps are included in the URL like so:

...&t=21s&feature=youtu.be&t=35

If the video is played from that URL, then it plays from the first timestamp, effectively meaning that the bookmark timestamps can no longer be updated with this addon.

Just added the add on to merely bookmark my video and my place in it and it seems to work. I think u need to restart Firefox. The folder appeared in the far left of my bookmark toolbar. Thanks for the extension.