How to push multiple images which make a single "app"

Usualy the Docker Hub description and additionaly provided compose files on Github are used.
Docker Hub is image centric. You need to externalize “the glue”. This is how it works. If you don’t like how it works: raise issues!

There is an established solution: continue to commit on Dockerhub and start using Kubernets + Helm Charts. Helm Charts are a well established and broadly accepted.