Azure Table storage is a key/value store similar to Hbase, Cassandra, GCP Bigtable, AWS DynamoDB and others. It's a very stable and scalable design which is why everyone has some version of it.

There's no way to add indexes to this data model, it's all done by just writing your data in another table using the key you want and the value pointing to the original table's row. Perhaps Azure could offer secondary indexes like AWS DynamoDB does but it's probably too complex of a feature to add at this point, which is why it took DynamoDB several years to get to working GSI.