just an annoying sidebar with no function
Firefox already has multiselect tabs built in, just Ctrl or Shift click on tabbar and right click to select your action

Still very useful with Waterfox Classic :-)

For some reason I spent a long time (months) ignoring the extension, now I realise that it includes a highly desirable feature:

- move tabs to new window.

I mentioned the extension as a workaround here:

https://redd.it/cgncgc

Seemed like it would be useful to move a group of tabs to a new window, then use Bookmark all tabs to save them to a folder. Somehow I ended up with about 3-4 new windows, some of which just had a blank tab. One of my other tabs became unpinned and all my tabs got rearranged. Firefox asked if I was sure I wanted to close 126 tabs (certainly NOT - no idea what triggered that). Got my tabs back thanks to a sessionstore backup. Hope this was a major anomaly, but I'm uninstalling. If you choose to use this, be very careful. At the very least the add-on needs some documentation on how to use it, and that needs to be in an easy to find location, preferably right on AMO.

Do nothing useful! Awful

I like the idea of this addon, but the developer needs to expand the possible actions you can do with multiple selected tabs.

Opening all of them in a separate window is great, but for me it would also be really great to be able to create a set of bookmarks for these as well. I used to use Tab Mix Plus and the biggest advantage for me was the "Open Closed Tabs" function and a session manager where you could save a set of tabs to reopen later.

How would that work? After you'd picked the tabs to save and selected "Save to Bookmark Set" (or equivalent) You'd be asked for a set name. and the addon would create that a folder by that name under a certain bookmark folder (maybe predetermined, or the user could set this up to a default location, so that it could say, be under the bookmarks toolbar) and add bookmarks for each tab selected. Those could then be edited if needed like any other bookmark.

Just an idea.

Allows you to move tabs you select to a new window