4) I did not find the option to cancel/disable file transfer. For example you and I use Dino. I can send you file even you do not want it.
Dino IM is good project but not for Whonix. Editing of messages, convenient management of PGP/OMEMO, history synchronization between devices, temporary keys. It’s very nice. But it’s provided through the reduced privacy and security.
All issues from my last message are at Github tickets for a long time. Developers are not ready to change something.