How to prevent a role from creating a file at the File Library root? about directus

[nicksergeant]

@hanneskuettner awesome! Thanks so much for the workaround here - that does indeed work 👍.

[hanneskuettner]

The problem here is that the folder field is not transmitted on item creation and is therefore undefined and not null.
I opened a separate issue #22278 that aims to deal with the problem of detecting unsubmitted fields.

For your situation a valid workaround seems to be to set the field preset to

{
    "folder": null
}

and then use the _nnull filter.