Transit Gateway - defaults

Is it possible to update an existing Transit Gateway to alter the default route table used for association and/or propagation?

My customer wants to use these default features but needs them to be different tables. When creating a TGW it seems you cannot get it to create 2 separate tables for these settings. Hence i would get one auto created and then hope to be able to update the TGW afterwards to change one of them to a different table.