In Chrome, goto the URL chrome://flags/#tab-groups, set it to enabled and relaunch Chrome. Then, you can right-click on tabs to add/remove them from a group. Or, if you open a link in one tab in a new tab, they'll automatically because a group. But, as you will see, they're not stacked and the group name takes up a spot in the tab bar. Something like this might be easier/possible for Opera to implement. But, it's not as good.

For now, you might find an extension at https://chrome.google.com/webstore/category/extensions that can manage tabs. There might be one that groups or stacks them. But, the groups or stacks will probably be in a menu or something when you click the extension's button and not on the tab bar.

@olfox1 I guess it was dropped because it never really worked as should.

Then ... what if the developers launch it again and make it work as should then? i mean, is a nice option to have, even if you want if some people dont like it u can disable this option i guess? but i would like to have the option of stacking, it was such an awesome feature .