it works Rated 4 out of 5 stars
the button appears in extra bar (at botton of browser window) ONLY when there is a tab with the exact same url as any other
to improve it..., the owner of this addon should allow user option treat urls with anchor or query as the same.
Rated 1 out of 5 stars
didn't find the button mentionedThis review is for a previous version of the add-on (0.12.1-signed.1-signed).