I’ve tried to manually port my RH5 settings over to RH6 so that I can finally start doing ‘production work’ 
I cannot seem to find a setting to control how I can select objects with the mouse. Example scene: two boxes ‘behind’ one another; one tall, and one short. In front view, I try to windows select upper left to bottom right around the short one only. Both get selected. That is, it behaves as if I cross-selected from bottom right to top left. The “Mouse group select” is set to Combo, as it is in my RH5. Looking in the “Settings Editor” (that looks like a handy new addition, by the way) and searching for “select” there doesn’t appear to be an other setting to control this.