https://stackoverflow.com/questions/10077987/visual-studio-2010-name-of-document-tab-context-menu
"Note, in Visual Studio 2010 to add a command to the right-click menu of a document’s tab, first you’ll need to right-click on a Visual Studio document tab to work around a Visual Studio bug. (Otherwise the Easy MDI Document Window context menu doesn’t show up in the Customize dialog.)"