Could the Default Set of Keyboard Shortcuts include "Edit > Select > Clips to End of Session" please?
It's a useful function.
Adding a custom shortcut isn't straightforward and can be hard for people new to Audition.
I don't think it's particularly difficult at all: Open up Keyboard Shortcuts, select Edit and scroll down to the option you want. Click on the shortcut space next to it and hit the key you want to use. Save the result - job done.