Authors (and Editors) can upload supplementary files by going to the submission's Summary page, and clicking the "Upload Supplementary File" link.
for some reason our Authors are not able to "Add a supplementary file" on the Summary page, after they have completed their submission. Yes the Editor can. In fact, at "Step 5 Confirming the Submission
" of the submission process we have introduced text to the effect of "NOTE: Once you click on Finish Submission, you will NOT be able to go back and make changes to your submission. Please therefore ensure that you have uploaded all of your documents, and that you have removed all identifying information from any documents that are intended for peer review.
So - the Author can return to Edit Metadata, but is unable to upload Supplementary Files. This must be in part the early rationale for including the above Note on our Step 5. But, I see here that the Author should be able to return to do this. I don't see any switches in Journal Setup that enables/disables this ability. Where then might I look to "turn" this on?