No, I don't believe you can.
What you could do though is filter it out completely; from
SQL Server Management Studio Schema View
In SSMS 2005 or 2008, right click on the heading: "Stored Procedures", "Tables", etc, then on "Filter Settings", then for the "Schema" change "Operator" to "Does not contain" or "Contains", etc and then set a Value to filter them...
I've just checked and it is still applicable in SSMS 2014
You would need to remember that is is there, though. Calendar reminder?
EDIT:
Ah, I miss-read the question. I was looking at other methods of ordering the list. I'll leave my answer here as an option, but I acknowledge it wasn't what you asked for.