This is a bit of a cheat, but I’ve developed a Shortcut that uses Siri to add an item. Actually, it doesn’t add via Beorg, but rather takes advantage of the fact that Beorg files are just plain text. It depends on having your files stored somewhere Siri can write to, e.g., Dropbox. If you ask Siri “Add to Inbox” (or whatever you call it), Siri will ask you “What text?”. When you pause, it will add
* TODO Whatever you wrote
to the bottom of Inbox.org. It closes by telling you “Done”. Next time Beorg syncs, there the item will be. It would be easy to add more functionality, like choosing the target file, but I wanted something that could be done entirely verbally and fairly quickly (it does take Siri a tick to be ready to take dictation).
An image of the shortcut (it’s really short) is attached. I hope it is useful to some.