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
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.
post edited by Samuel -