Ability for authors to upload additional files with manuscripts JDD

[kistrand]

Is your feature request related to a problem? Please describe.
It's very annoying an needlessly complex that the JDD lacks a feature for authors to submit additional files, such as supplementary material, responses to reviwers etc, when submitting a manuscript (or revised manuscript) to the JDD. Now they end up contacting me and then send the files for me to upload to the JDD system. This is an unnecessary and avoidable step imo.

Describe the solution you'd like
Add a feature for authors to upload more files other than just the manuscript to the JDD system.

Describe alternatives you've considered
I checked whether I could add this feature myself through the manager but I had no way of doing that.

Additional context
I see this as an urgent request