I don't have a Save as Draft button on the new listing form. There is only Preview or Publish.
I just made two listings and saw the draft button. I never use it so I can't say if it's working.
Just checked and I have a "save as draft" button at the bottom of the listing page if doing a "new" listing or using the "copy" feature.
@AAANativeArts It seems you have either clicked on an expired or a sold item and with either there is not a "save to draft" button.
I only see 3 choices, "discard changes", "preview" or "renew with changes".
Once an item has been published, there is no draft button. You can either relist it or leave it where it is and probably lose all your changes.