Essential extension - rely on it completely. Superb. Rated 5 out of 5 stars
Allows you to create a second bar containing tab groups. Immensely configurable, very very powerful - keep all tasks in separate groups and switch between them. Suspend groups for memory saving, or drop them to a "hibernated" list for later retrieval. Full drag and drop - everything. If a heavy tab user this extension will change your life.
Main point is, it will need configuring. The current tab color, read and unread tabs, when to open a new group and whether to automatically prompt to rename it, session backup options.... expect to play with these, but once you find the setup that works for you, it's a game-changer. I use it with Tab Mix Plus and Vertical Tabs and they're all compatible.