The add-on advertises itself as letting you open, copy OR bookmark multiple links AT THE SAME TIME, So where is the option to BOOKMARK multiple links at the same time? (Or to copy them, but I'm mostly interested by the bookmarking possibility.)
PS: Found the option in "Add Action" but for it to work, one must delete the "open as multiple tabs" action listed before. Just toggling it in the little black submenu doesn't work. It bookmarks the selected links in a folder called "Linkclump" with the date and hour, and to find it I had to use the "Bookmark Search Plus" Add-On. The order of the links is inverted though. I wonder if they would be in the right order if one selected the links from the bottom instead from the upper link? (Tested it. No, it is still in inverted order.)
I will still give you one star because you didn't explain any of this, and I almost rejected the add-on because of that.

When I use this ext to open either a single or multiple links at once it takes me to the new tabs rather than letting me continue browsing on the orirignal tab. I have double checked the settings and nothing I change in the settings alters this behaviour. This Ext works fine in Edge and Chrome so Firefox has the worse version. This make this ext completelyuseless for me.