I'd much prefer to be able to Cmd/Ctrl+Click tabs to select them, or Shift-Click a second tab to select a range, but that's not what this add-on does. If has a toolbar button that shows a list of tabs and checkboxes, and a button to select what action you'd like to take on the selected tabs from the list. Not ideal, but could be workable... could be... if... the system didn't have such a unreliable click handler for the checkboxes. It seems impossible to select more than a few tabs before another click on a checkbox deselects all the other tabs.

This makes it unusable.

All it has to do is let you click checkboxes, and it can't even do that right in this version. Save yourself some time and heartburn and look for another solution until this one gets fixed.