Since upgrading to from 2018.12.x to 2019.8, whenever I use a segment mode tool, it automaticall selects multiple tracks (audio & video) in the timeline.  I can't seem to find a way to drag just one track.  I've disabled sync locks and searched through all the timeline settings but can't find a way to select just one track.  Any advice greatly appreciated.

Sorry if this has already been covered somewhere on the forum.

Sounds like "Link Selection Toggle" is active? If your timeline buttons have the default layout then it should be between "Lift" and "Mark Clip".

Thanks Cutyes!  Yes, that was it.  I had inadvertently removed/replaced that button when customizing the new interface.