Hi Jay,
Sorry to be slow. I am supposed get postings to this group sent to my email, but somehow missed this one.
Yes you are correct and GEDitCOM Editor help says "merge with" is "not implemented yet" for internal scripting. That is an oversight and not hard to fix. I guess I just never needed it, but sounds like you could use it. I will implement for next version.
I found a bug today that needs a new positing so won't be too long (a couple of weeks maybe?).
John