@andrew84 - ah, yes, that would be even handier - I use pretty much everything else, so had not thought that wide.
If the messengers would behave as they should I wouldn't really mind, but since they seem to turn on whenever they feel like it I need them gone.
I'm currently tweaking out Vivaldi to see if the Tab Stacks suit my needs and how the browser performs. It may be that I won't have to worry about Messengers at all very soon. I may miss certain other aspects of Opera, but I'll be able to focus better on the tasks at hand without interruptions and that is the primary goal.
@sgunhouse --- yea, sorry, incorrect answer. Not an option there.
You should be able to right-click on one of the dividers like 'Today' and there would be a context option to not display in groups, but it is missing.
As I was writing this, I found the context menu I needed...
I had to collapse the groups and r-click in the blank space and finally found the group-by menu..
4 other browsers on this particular machine, and they are all fine.
Opera and Opera GX, not so much, but, problem now solved.