No additional configurations are required for exporters. If “pull” metrics mode is used than ports 4200[0…] have to be opened for your pmm-server on a monitored node.
I’ve been looking inside the entrypoint.py script and it seems that there is a way (but not documented) to inject a prerun script that does the job of post startup actions like adding more services/exporters.
The prerun script has to be included inside docker-compose yaml file via environment variable PMM_AGENT_PRERUN_SCRIPT following the path to your custom shell script.