If you deviate from anything Wappler standard, chances are you'll end up fighting Wappler. This is why I moved away from Wappler Docker deployment.
Anyway, answering your question, see the template below:
services:
<service_name>:
image: <image_name>
volumes:
- <host_directory>:<container_directory>
If you use bind-mount, don't give your volume a name, as exampled above