I have just gotten back to using Sonar from earlier versions from a while ago. In Piano Roll View you used to be able to drag across a measure to play the notes or stop on a multi note chord to hear it. Is this function available in Sonar Platinum?

Yes it is, with many new helpful features added since you last used it.

In the features section for Sonar Platinum, there is a short video explaining all the features of the PRV (Piano Roll View), including the "Smart Tool"
https://www.cakewalk.com/...s/SONAR/Features#start

Thanks for helping direct me where to look further. The following (Scrub tool) is what I was looking for from:
 
 Cakewalk // Documentation // SONAR // Scrub tool (sorry I cannot post URL's here yet...)
 
The Scrub tool lets you audition all displayed tracks as you drag the mouse cursor forward or backward at the desired speed. You can scrub a single track by dragging over the track, or all displayed tracks by dragging in the Time Ruler.
 
To scrub a single track - Hold down the J key to temporarily enable Scrub mode and drag over the track.
 
To scrub all displayed tracks - Hold down the J key to temporarily enable Scrub mode and drag in the Time Ruler.