Thank you for the quick answer!

Unfortunately, I'm going to store the dynamic access token value in that environment variable. The token need to be generated per cluster and will expire in 4 hours. So my environment variable value is known only on cluster setup. That is the reason why I used the init script. So the docker image creation will be to early.

Does Databricks have the environment variable storage which will be injected before each notebook run? That will be the perfect solution for me.