I have two add-ons which are crucial to my use of FireFox, and I am looking for a compatible third add-on. The two add-ons that I use (which work together) are "Vertical Tabs Reloaded" which allows me to see my huge number of tabs vertically (as a left-hand, always-open, resizable window) and "Duplicate in Tab Context Menu" which allows me to duplicate a tab complete with history and filled in forms. The add-ins that I have found so far, either set up categories of tabs as tiles or as menus. I need to be able to combine tabs into tabs instead. That way, I can see everything in my single vertical tab list, yet shrink the tab list so that I do not need to scroll so much. Can you suggest such an add-in? Appreciatively, David D.