On my end, I tried adding a contact with Share extension to Agenda. This is what happened:
From iPhone to Mac
On my iPhone 8+, iOS 14.4.2, Agenda 13 (182):
Works. An icon is added to the note. If I click on it within Agenda (i.e. without switching programs) the contact opens with all data and profile photo.
Works as above.
Only the vCard file is inserted as plain text. Since the contact has a photo, this results in about 2.5 m of text to scroll… The first time I tried this, Agenda crashed.
I synced this agenda note with my Mac (macOS 10.14.6, Agenda 13 (182))
The contacts inserted from Cardhop or ContactsXL on my Mac behave the same:
Only a thumbnail of the contact is displayed. Double clicking on it wants to add this contact to Contacts.app or BusyContacts.
Quicklook does not open the contact, it shows a preview window with a lock in the icon, so it is locked and does not show any contact information. If the contact contains a profile picture, at least it is displayed.
The contact coming from the native Contacts.app shows the same long vCard text.
From Mac to iPhone
The other way round: contacts are inserted on the Mac side and synced with the iPhone:
BusyContacts unfortunately does not support sharing capabilities for non-Apple applications.
Cardhop has a sharing feature. I can select the note in Agenda to save the contact to and click „insert“. Then the window freezes, I can’t click „Cancel“ or „Save“. I have to shoot down the process „Agenda : Cardhop“. Nevertheless the usual but unfortunately useless 2,5m vCard text is inserted.
Contacts.app shows the same behavior here as Cardhop.
I don’t have a chance to try this thing on the iPad right now.
Conclusion: No possibility for boredom for you. Or the feeling that Agenda is now finished…