Sometimes, after editing a pipeline or orchestration file in the XML Editor, Visual Studio will not open that file in the default pipeline or orchestration editor. Instead, it opens the file in the XML editor or a text editor.
To help Visual Studio “forget” this behavior, close the solution and open the appropriate .btproj file(s) in Notepad. Delete the <SubType>Designer</SubType> nodes from the ItemGroup element associated with the file(s) that open in the wrong editor, then save and close the .btproj file.
When you open the solution again, the file(s) will open in the expected editor.