To end your text entry, type a . as the first and only character on a line.

The following other commands are available in text entry mode.  They must be
entered at the beginning of a line, but the names may be abbreviated.

  $:edit                - invoke your editor on text entered so far.
  $:/<old>/<new>        - replace occurrences of <old> with <new>
  $:quit                - abort text entry.
  $:spell               - check spelling
  $:ok                  - end text entry and prompt for verification.
  $:clear               - clear buffer, deleting any text entered.
  $:print               - reprint the text you have entered so far.
  $:read <filename>     - append file contents to your text.
  $:write <filename>    - save a copy of entered text to a disk file.
  $:set [<option>]      - display or set options
  $:help                - show this help message.

In addition, Control-L will reprint your text and may be entered anywhere.

For more help, do !man gate