The (surprising) absence of this feature just came to my attention, as I was filling in a contact form for which autofill did not work (because whoever designed the form used nonstandard field IDs, like fox-c1160-textfield5). “No problem,” I thought – “I’ll just open the identity item and copy the information using the copy button” – I was surprised to see no functionality whatsoever available on the View Item screen for the default fields of an identity item.
I suppose a workaround would be to duplicate each default field using a “linked” custom field, but this would be a cumbersome approach, and it would still require me to scroll down past the default “ITEM INFORMATION” section to get to the custom fields.
I have added my vote to this request.