After following the steps detailed in Opening an EDI File, use the resulting window as you would any other text editor. After modifying the text of the opened EDI file, the Save button on the Top Menu bar and the TaskBar will become enabled. Click this to save your changes to the EDI file.
The EDI Editor work like any other WYSIWYG (What-you-see-is-what-you-get) editor, you can navigate, cut, copy and paste.
The Keyboard short cuts like Ctrl+C, Ctrl+V, Ctrl+X, Ctrl+Z and Ctrl+Y for Copy, Paste, Cut Undo and Redo work of course