I am indebted to David Fronk, Dynamic Methods Inc. for this article:
http://dmcrm.blogspot.com/2008/01/adding-notes-or-activities-to-existing…
“After a bit of searching and a random idea about reimporting my XML into an existing entity I found my answer. I exported the entity XML hoping to import it on top of an existing custom entity that had Notes and Activities enabled, I got an error however regarding type codes not matching or already existing. So, I went through the XML and as I was searching I found some tags (that you can see very apparently in one of the Sonoma screenshots of their post) called:
HasRelatedNotes
HasRelatedActivities
I then had a crazy idea. I deleted my old entity, published, changed the HasRelatedNotes tag to True (or 1), imported the “new” entity and I then had all 150+ fields, form setup and scripts as before only this time with attachment capabilities.
Now take this one step further and you could even copy an entity by modifying a few tags here and there so that the “copied” entity has a unique name, entitytypecode, and identifiers. I’ve done this a couple of times and I have to fight errors about things already existing but for the most part the errors were decent in letting me know what I has messed up…not necessarily where though. It’s great for larger custom entities that need to be extremely similar.”