Clip vs. session marker

had the same problem - found the answer here - seems to work - apparently you deselect all tracks and hit m to get the session marker: https://helpx.adobe.com/audition/using/clip-markers-for-multitrack-in-audition.html

(annoying as hell to waste an hour of my life solving the problem while trying to create and record). 

Not that I'm aware of - it's hard wired; there's no reference to it in Keyboard shortcuts and no option to alter it in Preferences. Also, it's not a change in the new release; the previous release did exactly the same thing. I can't say that I'm that surprised about the behavior either - people have been banging on about multitrack clip markers for ages with the idea that they'd be a lot more use than Session markers, and personally I think this behaviour is a reasonable compromise - obviously YMMV...