Write an OnSetBookmark event handler to initialize new bookmark created when you assign to the Bookmarks property. 

OnSetBookmark occurs only when:

  Bookmarks[N] := M;

when there is no bookmark with the index N and M <> -1. 

Assigning False to Accept will destroy created bookmark and will prevent new bookmark insertion. 

Standard bookmarks (indexes: 0-9) are inserted by means of assigning to the Bookmarks property, so use OnSetBookmark to initialize standard bookmarks (see Main demo of the library).

TCustomSyntaxMemo Events