I try to activate a rtf file in Devonthink so I can get my curser set in the free field and then insert my snippet there. The rtf file always has the same name.
In DEVONthink, if you select an editable document (e.g., your file) and press Control-Tab your cursor will move to the end of the text in that document. Your macro could do the key-press for you and pause a second.