@joannaczajka its the tab island of websites that i will open maybe in a few hours or several days. Not a website that i will want to save, cause that will be saved in the favourite bookmarks.
For example. Automatically opera will make a tab island for me, or i make it manually. Then i open another tab/tabs (not in that island) and a few minutes or 5 have past, and i never click on any previous websites that are in that tab island, the tab island then minimize itself. Saving tab room.