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.