Ctrl+B sets bookmarks, with Ctrl+Left; and Ctrl+Right you can move between the bookmarks. The pulldown "bookmark/open bookmark list", or Ctrl+Shift+B, opens a list of all bookmarks for the current dictation. There having ticked "prompt for comment when setting bookmark" you will be asked for a comment every time you set a new bookmark, later shown in the bookmark list. e.g. You want to enter: "Continue from here" or "Did you mean NIGHT or KNIGHT?".
Click the Remove button on the Bookmarks dialog to remove a selected bookmark from the list.
Note: The DCT file format does not currently support saving bookmarks.
See also:
Using Express Scribe with your Word Processor