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.
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.