There is no way to concatenate values in Adobe Analytics (unless you set up a new dimension explicitly for this purpose, which will only work from the time you start tracking a value).
I assume this is related to your earlier question about multiple dimensions in the API to simplify the work... this won't help you for historical data, but you could quickly create a concatenated eVar in Adobe Launch or with Processing Rules and start collecting data from now on...
I believe you can concatenate in CJA (Customer Journey Analytics), but that likely doesn't help you.