Yes, and this is what you have to add (don't remove the existing youtube button whose definition can be found on the context sensitive Admin Help file):
Pattern: \[(tube)\]http\:\/\/youtu\.be\/([^\[\s]+)\[\/\1\]
Example: [tube]http://youtu.be/1234
_56
[/tube]
Everything else will be the same as the existing youtube code, i.e. the code shown
here.
Then, you will add editor buttons for your WYSIWYG editor for this new code. Copy everything from the old one and save, and then set the old code's editor button to "don't show".
Also you can add a editor button for youtube too. See
this link for more info.
Demo:
post edited by Samuel -