Actually I was able to get what I needed from my backed up Tabs file using this https://github.com/cclgroupltd/ccl-ssns/issues/9#issuecomment-633979933

@leocg I'll perform a deep-scan disk recovery. Which files do I need exactly? Is it both the Session and Tabs files?

Well I'm not opening Opera again until I find out if it's possible to recover this.

I think I really misunderstood how workspaces work. I thought they were like a universal saved list of tabs, but then I read that they're actually saved per each window. Oops.
So I closed out of each window after stowing the tabs away in different workspaces, as before, I had like 6 windows open with many tabs.

Well....
What can I do?
I've opened and closed Opera once since then. I found Session and Tabs files in the Sessions folder.
?