This backend version is not supported to design database diagrams or tables. (MS Visual Database Tools)

From previous I try to change table field size in SQL Server Management Studio I got this message appear and can't change anything with my table so I realize I use Server Management 2008R2 but my Database version is 2012 for now so I change Server Management to use version 2012 and it work fine. to avoid this don't use old version to edit new version that's all.