Since it took me multiple searches and time to arrive at the workaround for this particular bug, thought I'd make a separate post for you, user from the future.
Summary of the bug: When you try to create a 6th workspace on Opera's desktop browser, it renames one of the 5 existing workspaces instead of creating a new one.
Workaround: Right-click Player (the Special Feature that lets you listen to YouTube Music / Spotify / etc., in the sidebar itself), then select Hide Player. Now try creating the 6th workspace. Should work.
I am on Opera version 97.0.4719.63, and can confirm that:
- I was unable to create a 6th workspace until I hid Player.
- After creating the workspace, I re-enabled Player, and the 6th workspace persisted.
Hope this is useful.