@leocg you do see that Workspaces don't provide the same speed as tab grouping, as shown in @hien-reese's post, right? Workspaces are very useful, but tab grouping is indeed missing from Opera.
Right now for example, I have 2 pinned tabs (Google Drive and Gmail) and 6 different (but all work-related, so all in the "Work" Workspace) sets of Spreadsheets and Code open right now. These sets change pretty much everyday, for me. I would love to be able to separate them into quick groups, both so I can read the name of the files better and so I don't mix up which Spreadsheet tab is which, since they all have the same Google Sheets logo on them. But without groups, I can't do that.
If I went for a Workspaces approach to this, I would have to create 6 different Workspaces each with about 3 tabs open, all of which would be work-related and only relevant to this work-session (thus I would have to delete those Workspaces later, since they'd lose relevancy), and also missing my pinned tabs. Once again, Workspaces are very useful, but they are more akin to having multiple browser windows open at the same time than what tab grouping provides.
Is there any place to officially provide feedback/feature suggestions to Opera? I'd appreciate if you could link that here, or otherwise pass the suggestion onwards to the appropriate team, if you have access to that.