Drafts are not saved to the process variables, they're just a save point for the user to pick up where they left off, so there's no change as far as the process is concerned until it's actually submitted.

Think of it like an email draft; it shows up in the Draft folder, but not in the Sent folder, or the recipient's inbox, because it's still a "pending" action that hasn't been completed yet.

If you want "draft" changes to be tracked, then the changes need to be submitted so you should:

1. Disable the normal save as draft option because this isn't tracked activity
2. Add another button to the user task form in addition to approve, submit, etc.
3. Call the additional button "Save Draft" or something similar
4. After the user task, add a gateway
   • If the action was "Save Draft" loop back to assign the task back to the user
   • Else (default path), continue to the next step in the process

Basically, what this does is submit the "draft" changes to the server so the variables get updated and those changes can be tracked in reporting without necessarily continuing onto the next step.