Possible to change modalities after assistant is created?

Hi! Was hoping I could get my flow down in text and then change it to voice, but I don't see a way to access that setting. Could someone confirm this is or isn't possible?
Related question: If I can't change this, I thought I'd create a new asst with voice modality and then copy clone link from my text project into voice project, but doesn't seem that works either. Just looking for comfirmation if anyone has it--thank you!