I understand. I don't mind, because I keep single window and use those groups like windows. But I've been lucky with not stumbling upon weak persistency, so I g

I understand. I don't mind, because I keep single window and use those groups like windows. But I've been lucky with not stumbling upon weak persistency, so I get how it could be frustrating. Warning about tab hiding is normal. I assume that something that you would find perfect also would have to use tab hiding. They need more work or something separate, because the manual resizing of groups seems like a busy-work. I would like something more like Simplified Tab Groups, but with good syncing as you said. I'm not sure how would it work with current Firefox APIs though. If extension shows you the same group for two separate widows, what would happen if you would select the group in both of them? It would have to create additional tabs so they would not be shared. Also I'm not sure if tab hiding API allows to mix tabs from different windows. I think that what you want is not possible currently as an extension.