How can I see two folder trees?

I've just upgraded to DOpus 11 and the dual display no longer shows dual displays. The folder contents appear in two windows, but there is only a single tree.
I find this frustrating, because the wrong folder's contents usually appear when I click on a folder. I tried clicking on the a file, then choosing a different folder, but I can't reliably display a folder like I could in DOpus 10.
I just tried to synchronise two folders and after 15 minutes was told that they are in sync. This was a surprise until I noticed that clicking on a different folder, after going to dual display, had not changed the folder.
How can I regain the second tree???

Turning on Preferences / Folder Tree / Options / Open second Folder Tree in dual display mode is usually all that's needed.

(It can depend how the windows/trees are opened, if that doesn't do it on its own.)

Thanks. I found that eventually, I wasn't expecting the default to be that turned off.

Is there any way to position the second folder tree to the right of the second folder panel?

Folder Tree | Folder Panel | Folder Panel | Folder Tree

No, not in general. There's only one situation where the tree will appear to the right of its file display (dual horizontal file displays with a tree turned on for the bottom one but not the top).

Thanks Leo. That being the case I think it could be a welcome addition. IMO it's easy on the eyes while using the second tree. I'm guessing most of the action happens in the Folder panels, so it makes sense having that bit of the GUI as close to the part of the screen that is most ergonomic for the user i.e. the left-to-right center of the screen. Also, since dragging files between the left and the right is presumably a common action to perform, it would make sense to keep the bits of of the GUI where the file or folder is picked up and the bit of the GUI where it is dropped as near each other as possible (ideally side-by-side). Having to drag the file over the second folder tree IMO challenges the UX and aesthetics. It's a bit like when you make battered fried fish: you dip the fish in the batter bowl and then from there transfer it to the frying pan—you want that bowl as close to the frying pan as possible to prevent the batter dripping all over the place along the way, and also to reduce the distance the food needs to travel. Similarly, by keeping the two folder panels close together, you prevent accidentally dropping a file onto a tree folder, and also improve the ergonomics as less mouse travel is required to move a file from the left to the right.

Having used DOpus over 17 years, I never realized this was an option! Not sure I would use it, but interesting nonetheless.