When I click "Transfer App" in App Store connect, I get "Apps built using Mac Catalyst cannot be transferred at this time." I googled and found: https://forums.developer.apple.com/thread/128023. But I also found:
Apps created with Mac Catalyst
In order to transfer apps created with Mac Catalyst that are not offering universal purchase, both the iPad app (primary app ID) and the Mac app (Mac Catalyst App ID) need to be transferred.
You will need to initiate the transfer for your iPad app first, and then the associated Mac app after. It is important to transfer the Mac app (Mac Catalyst App ID) to the recipient as they will not be able to create a new Mac app based off of the iPad app (primary app ID).
from https://help.apple.com/app-store-connect/en.lproj/static.html#dev9e1e9833d.
Is the above documentation outdated?
My app built with catalyst is available on iOS App Store, but I didn't submit to macOS App Store. Does anyone have experience in transferring Catalyst app?