It's the best addon for tab management, in my opinion. It has groups and folders , autosave(Tools=>Open Window Manager=>Autosave) and import/export sessions feature. If one "loses" its groups folders, it is really easy to get them back by loading and merging a previous (working) session into the current one through the autosave feature mentioned above. Previously i have tried Tab Center Redux then TreeStyleTabs + SimpleTabGroups(my previous setup).