https://addons.opera.com/de/extensions/details/tabsetsnet/
Tabsets.net-Erweiterung - Opera Add-ons
Use the tabsets.net browser extension to safely keep track all your tabs and links in the Side Panel, locally or in the cloud
erweiterungoperaaddons
https://bugzilla.mozilla.org/show_bug.cgi?id=180564
180564 - Creating bookmark tabsets with the same name gives no warning and doesn't replace
VERIFIED (sfraser_bugs) in Camino Graveyard - Bookmarks. Last updated 2002-11-25.