How to get the SDK class generator from OPT to allow term_mappings

I’ve been trying to get the openEHR SDK class generator to give me the option to add arbitrary TERM_MAPPINGS to an existing DV_TEXT (use case is add arbitrary maps to snomed codes for the name). I’ve tried to pass the OPT with the “mappings” attribute with several flavors (as a domain type (C_CODE_PHRASE), as a class
with the corresponding type name, with and without specifying a terminology,etc.)
Is there any OPT substructure that would allow this without knowing the specific codes beforehand?