To remove a gap in the Sanger Reads Editor select the next character or gap after the gap you want to remove and press Backspace. You can also select Edit->Remove gap at the left in the context menu or Actions->Edit->Remove gap at the left.
If there is a region of gaps or it is the beginning of a read, by holding the Backspace key, one can shift a Sanger read to the left. To shift the read to the right hold the Space key, see the Inserting Gap chapter.
You can always cancel the changes by pressing Ctrl+Z.