I use Opera GX because I like to have many tabs open and limit the amount of resources being consumed, something I can't do with Chrome. The problem comes when closing those tabs. If I right click on a tab, it gives me the option to close the tab, but right below that is the "Close other tabs" option. If I click it accidentally, I lose all other tabs. I can't recover all of the tabs, because the recently closed tabs list only lasts for a short period of time and it doesn't go back very far.
My suggestion is to add a feature that opens all recently closed tabs at once, similar to how Chrome lets you recover tabs. With chrome, it will automatically recover all tabs when you close the window and it can be turned on and off in the settings. But if you open an empty window, and then close your the window holding all your tabs, Chrome will allow you to open all the tabs you closed recently. Either that, or remove the "Close other tabs option."