I would dearly like to recommend to the SONAR development team that they add a TAP button next to the tempo box. Nearly every time I come up with a new song idea I have to go to a different application that has a TAP button to accurately work out the tempo in my head. TAP button please, it would be so easy to do.

This is possible by using the menu item Project Insert | insert Tempo change.  You can also assign a keyboard shortcut to "project | insert Tempo change". 

You can also assign a button on the Custom Module on the Controller Bar to "project | insert Tempo change"
 
On the resulting dialogue box, there is a "Tap Tempo" button.

Ahhh. I did not know that was there. many thanks