Hey, Alex, I do not believe there is support for docker-compose.override.yml or any plans to implement support for it (unless there is user demand), so I think your solution should be fine, if you are just running some tests and don’t need a fully virtualized Balena OS environment (otherwise, see here).
Furthermore, when using docker-compose, you have the full features of docker-compose for extending as seen here: Share Compose configurations between files and projects | Docker Documentation .
This means you could do something like docker-compose -f docker-compose.yml -f docker-compose.dev.yml up as well, giving you even more flexibility.
Balena only supports a subset of these features for the sake of simplicity.