Just confirmed with my team—we don't support composite keys, unfortunately. Here's a community post my teammate found that might be helpful! http://community.retool.com/t/how-to-use-composite-primary-key-for-bulk-updates/2406/10
A workaround a past user did was write a query to update each row, then use a map to return an array of triggers on the recordUpdates object utilizing JS promises. Not sure if something like that could work for your use case?
Also, here is a feature request for composite keys, if you'd like to add your +1.