Elastic Agent - Fleet Server Configuration yml

Hello.

I was able to spin up Elastic, Kibana and Fleet server in docker based on the official docker-compose.yml and this repo. My setup is not intended for production use. It is used purely for my personal experiments and testing.

I wanted to keep Elastic and Kibana configuration in their respective configuration files, i.e., elasticsearch.yml and kibana.yml, instead of passing the configuration as environment variables. With the help of the documentation, I was able to achieve this.

However, I'm somewhat struggling with the Fleet server. The aforementioned repo uses FLEET_SERVER_ENABLE=true, and other flags, to enable the server. Just as described in the documentation.
I'd like to avoid using these environment variables and configure the server via configuration files, just like Elastic and Kibana.
I'm looking at the reference elastic-agent.yml, fleet-server.yml and Elastic agent's config structure docs but, unfortunately, can't understand if something like that is even possible.
The question therefore is: can I actually configure elastic-agent.yml / fleet-server.yml, and pass it to the elastic-agent container so that it runs Fleet Server as well?

Thank you.