@Starson - yeah I did warn about the config file thing in the post it is attached to, but can't blame you for not reading all of my ramblings
@Charles - I don't suppose there is a convenient way to identify what the current sort column is? I discovered that sorting every time you move to the next duplicate group is quite slow. So what would be better I think (since the topmost sort column is that of "marked") is to check whether that is still the current top sort column, and only apply my sorts again of title then marked if it is not. The user can't sort on "marked" since it is not visible, so this should work as an optimisation.
I know from my ViewManager plugin that I can get down and dirty and roll around in get_state() with sort history etc, but I thought I would ask you first before I did that again to see if you had a better suggestion