I thought references are publications, I inputed: PubMed20123456; 20123456; pubmed:20123456.
I don't understand unifing columns, you mentioned. But, genetic and generic-variant data overlays has identifier column which can be used as any identifier, for example: HGNC_SYMBOL:SNCA. Isn't references duplicate of identifier? If it is, then let's remove references column, the name is also misleading, like reference genome.