I can't get the OPENINLEFT or OPENINRIGHT option to work with the "Go BACK" command. Is there some other way to make a Back button that affects the left or right pane?
There probably isn't. I think the back folder history is stored separately for each file display (in fact, probably for each tab now that we have tabs) so the other file displays don't have the cached folder to display.
Maybe it should work, though, or at least make the other display load the same path as in the cached history. (So you would lose the scroll position, file selection and any changes made to the view mode, but you'd be able to load the previous folder of one file display into another.)
If that would do the job and you don't mind about the limitations then you should drop GPSoft a feature request via their support form.
Not sure I follow this. I mean, the folder history is available when I focus the pane, why not at other times? (Maybe I should mention that I always use a Commander-style interface with a left and right pane.)
Well, it's no big deal. I'm just trying out an idea I had, which was to make all my toolbar buttons - where it makes sense - to apply to the left pane with a left-click and to the right pane with a right-click.
I just mean that each pane stores its own folder history. (Which makes sense. If you press back in one pane you don't want to go back to the last folder viewed in a completely different pane, even if it was viewed more recently.)
Oh sure. I was just hoping to access the left or right pane like with many other functions (it works for "Up", for example). Well, just playing around with it for now - nothing crucial 
Oh sure. I was just hoping to access the left or right pane like with many other functions (it works for "Up", for example). Well, just playing around with it for now - nothing crucial [/quote]
"Up" works in both panes, because it does not need to be in the History for Opus to find it. With "Up", you are navigating relative to the displayed folder's location, not relative to its place in the pane's browsing history queue. Every folder also has an "Up" folder, except for the Windows Desktop.
You can tell Opus to use "UP Back" instead of "Up". This amounts to an "UP" command that will also search the current pane's history to see if the folder had already been listed, and if so display it like it had already been displayed. But this command will not pull history from the other lister pane.