I think you misunderstood the question. I can export the Metas from main site as json. When I import to subsites the metas populate but the Meta IDs are different. They run sequentially even if previous metas have been deleted. (Deleting 10 metas from subsites means that new import will start at 11 not 0). And to sync these metas – the IDs need to be the same on main site and subsites.
Is there some code to add to the JSON to force the subsite to use the IDs in the JSON? If not what is a better work around?