It turns out one can create "generic" "boot application" entries in BCD e.g. as bcdedit /create /d "Blah" /application BOOTAPP.
Looking in the registry hive, these have type 0xa=Generic application. But the odd thing about them is that they don't even have a notion of drive. If you try to bcdedit /set a drive for an entry of this type you get an error. So, what's the point of this type of entry in BCD? (Inheritance only? But of what?)