No. The “Allow Clipping” is automatically not selected. Generally this option should not be selected because it can cause permanent and irreparable distortion due to clipping.
If you need to make a track louder than Amplify will allow without enabling “Allow Clipping” then you should use dynamic compression (http://en.wikipedia.org/wiki/Loudness_war)
I actually meant to split stereo track which is under the Track Drop-Down Menu, not the one you reffered to. As I understand it, the best related keyboard shortcut is shift + M which opens the menu mentioned above. Therefore there’s no direct keyboard shortcut for split stereo track.