I am in the habit of doing all drums on one track then cloning and erasing all but the desired specific drum on that track (say the snare on one, kick on another, fills and cymbals on another - so as to process differently). Is there a quick way to do this other than running the cursor along the unwanted drums for the length of the song ? e.g. a way to highlight the drums at the start and click something somewhere ? Thank you.

https://www.cakewalk.com/Support/Knowledge-Base/2007013155/Splitting-up-your-MIDI-drums

If your asking if you can delete all of any given notes then yes, Just click on the associated piano key and that will highlight all those notes of that key. If you sweep the keyboard gui you can highlight all the notes too. 
This also works for any CC events. 
Say you want to lower the velocity of all the kicks. Klick on the Keyboard GUI to highlight all the kick notes and then use the smart tool to lower the velocity. 

I just use the Cal "Split notes to tracks". Been doing that forever.........Very quick
 
OK, after I posted I saw that's where the link above leads you. That cal has been around for a long time-for me it has been great.

Stratman, I posted a couple of times that the CAL file split notes to tracks has been broken in the CbB version!!!
Is it working for you because my workaround has been to raise the number of the track to split to by one. Otherwise, the kick is lost in the split. I, too, have used this CAL forever and now my most used tool is crippled!!!!
I don't know if anyone is listening but,
PLEASE, FIX THE SPLIT NOTES TO TRACKS CAL!!!!!!!
STRATMAN, please let me know if your CAL version is still working.