Probably I think it is difficult to delete.
You cannot currently delete Qlik NPrinting reports from the Qlik Sense hub.
Summing up: After opening a support case on Qlik support I was told that is works as designed.
Qlik's tech support's answer:
Thanks for your time on the phone just now.
As discussed, there is no way to delete reports from the hub as of now. If you see the gray box at the top of this page:
you will see:
Users cannot delete reports after they are published into the Qlik Sense hub. Reports will be automatically deleted based on the values of the Publish task parameters: Days to keep and Reports to keep.
Since neither Days to keep nore reports to keep can be 0 you will always have at least one version of the report available in the hub.
As information, even QlikView documents published to hub cannot be deleted (not just NPrinting reports). Please see the grey box at the bottom of this page:
The above is as designed according to R&D. If you would like to raise a Feature Request to change this behavior please follow the steps in the attached article [How To Submit Feature Requests For Qlik Products].
As there is not much that Tech Support can do on this issue, are you happy for me to close this case? Please let me know.