thank you for asking this question. I can confirm that right now you can only publish an app into a stream by using the QMC. But, we do have some improvements for the whole process of publishing already on our road map. One focus area is to make it easier to publish content as a developer who creates this kind content, without the need to go into the QMC for it.
So please stay tuned for upcoming announcements about new capabilities and improvements in that area.
Let me / us know if you have any further questions.