Hide\Show Column in Sharepoint Form

You don't need desugner to hide or show a column in Display, Edit and New form of Sharepoint List. You could use Sharepoint Objects to set this programmatically-

Create a console application and Reference SharePoint Library-
The code will be
SPSite site = new SPSite(SiteName);
SPWeb web = site.OpenWeb();
SPList list = web.Lists[ListName]; // Get teh list
// Colname = Column to hide\show
list.Fields[ColName].ShowInEditForm = ShowInEditForm;
list.Fields[ColName].ShowInDisplayForm = ShowInDispForm;
list.Fields[ColName].ShowInNewForm = ShowInNewForm;
list.Fields[ColName].Update();