This could also be scripted:
tell application id "DNtp"
set theSelection to selected records
if theSelection is not {} then
set theMergedRecord to merge records theSelection
set custom meta data of theMergedRecord to custom meta data of item 1 of theSelection
end if
end tell
Well, theoretically… due to a typo in the AppleScript suite of version 3.8 the merge command isn’t available. The next release will fix this of course.