As of now, We don't have flexibility to add custom fields in both Create Incident or Create Incident with Identifiers. As you know, there are lot of different customization happens in most of the ITSM forms.
We can use Create Entry if it is customized but Incident status is not in sync if we use Create Entry.
It would be very helpful to add this feature in future versions. So, that Custom ITSM applications can use the Create Incident or Incident with identifiers and Status will be in sync. Please let me know your thoughts on this.
Thanks and Regards,