“save and continue” with file uploads

The ability to “save and continue” entry of a form is really useful, but if the form has “File upload fields” any files identified before doing a save are not recorded and therefore absent when continuing later.

I appreciate it does not make sense to actually upload the files until the form is submitted but I would like to warn my users that any they have entered will be lost by doing save.

I had considered that could be done by adding an error in filter “forminator_custom_form_submit_errors” but that does not appear to have any way of telling that it has been called for a “save” rather than a “submit”.

So:

• Should the standard product warn that files marked for upload will be lost by doing “save”?
• Is there a way to determine reason “forminator_custom_form_submit_errors” has been called?
• Is there a better filter to use?