MDX designer is equipped with intellisense. 
If appropriate while you are typing intellisense 
window
will appear or not.
When appears you may use two keys to use 
intellisense suggestion:
§          
TAB                                       
returns only selected keyword
§          
ENTER                                 
returns keyword and code snippet id appropriate
Let us see what will happened when you type "cro" for Crossjoin 

If you use ENTER you will 
get cod snippet for CrossJoin:

If you use TAB , you will get only 
keyword CrossJoin: 

More: