ToggleBookmark sets or clears bookmarked locations.
procedure ToggleBookmark(Index: integer);
Number of bookmarks is unlimited. Bookmarks let you save your place within a long text file. You can also press Ctrl+Shift and the number of the bookmark to set or change the location of a bookmark. When a bookmark is set, you see a gray box in the left margin of the Code editor with the bookmark number in it.