To insert a gap into a read in the Sanger Reads Editor select a character or a gap in the corresponding location in the Chromatogram Area and press Space, select Edit–>Insert gap in the context item, or Actions->Edit->Insert gap in the main menu.
Thus, by holding the Space key, one can shift a Sanger read to the right. To shift the read to the left hold the Backspace key, see the Removing Gap at the Left chapter.
You can always cancel the changes by pressing Ctrl+Z.