I have just tried to follow the Help topic at https://support.mozilla.org/en-US/kb/what-are-tab-groups#w_how-do-i-create-a-tab-group, to create groups of tabs relating to same subject, ready to save the tab group as a Favourite/Bookmark. With the Tab Group view open it says "To make a new group, simply drag one tab out of the group and then drag a second one on top of it. A box will be drawn around them." Looking at the screenshot accompanying the instruction, it appears that the selected tab from the group view is 'dragged' on to the Desktop (it doesn't actually state where to drag the thumbnail image of the tab to in the instructions). As soon as the thumbnail image is dragged outside of the tab group view panel - i.e. towards the Desktop - a black 'no entry' symbol (black circle with black diagonal line across its diameter) appears over the thumbnail & when the left mouse button is released the thumbnail 'snaps' back into its original position in the tab group view panel. What am I doing wrong?