Move tab to a new window already exists, it's a cool feature. However, there should also be "move tab group to a new window" feature. In this picture as you can see I have to individually move all the tabs within a tab group to a new window. So if there are 10 tabs inside a tab group I have to move each of them one by one, and then I have to drag and drop each of them to the main tab group's head tab and rearrange their order.
