In addition to a full synchronize (as provided by the panel) I really like a trivial 'one-key-select' action for the two dualpane folders that can be used to quickly select all elements in each pane that differ (date or size) from the elements on the other side.
This may cover most of the simple synchronize cases and may boost-up your workflow. I know this from other file explorers and I have used this hotkey heavily in 3 of 4 cases as alternative to the actual synchronize feature.
Is there any way to achieve this with the current version of DOpus?
We have a command which will show you the missing files between two folders. (Not files which are in both but, though.)
We also have a command which will do the actual copy you are looking for (without showing you the files selected first; prompting you for any files it will replace one by one).
There's no way to do exactly what you want currently but we'll think about adding it.