(Note, I previously gave this a 1/5 rating because it was consuming a lot system resources & making my browsing virtually impossible). However, after much experimentation with the other addons, it turns out, the cause was another extension for youtube that was interfering with this addon. Upon removal of that extension, oneTab is working just fine. So thank you to the devs. My one complaint is that its UX is quite strange, I would have liked to be able to save the tabs (which we can rename already) and move between the groups, similar to GroupTabs. Regardless, I am taking my time to get used to this addon. Thanks again. Rating revised.