I got this from Becky at Genome Mate a little while ago:

"You should now be able to merge multiple gedmatch kits into one relative record.

I don't merge match data as that can get me into all kinds of trouble and it will just get added back the next time CoA is loaded. What I recommend is that people hide the matches they don't want to see. I will add an option to autohide those for the ones that already have shared matches in a future release."

Jim