Added java 11 to docker-agent - now want to select it in the JDK drop down

I'm using the standard docker agent image (jetbrains/teamcity-agent), and went ahead to add in an older version of java so that I can compile my code with this rather than the standard 17 that comes bundled (used these instructions for guidance). 

The new java version is living in /usr/lib/jvm/java-ll-openjdk-amd64

So now I want to be able to refer to this java version in my build configuration - which I realise is an issue if this is on the agent, but not on the server. I'm planning on adding several more java versions in the future so that I can test that the code can be compiled in the different jdks - so this isn't a once off. 

How do I define parameters on a docker agent that will then be communicated through to the central server (also running in docker at the moment)? If this is how to solve the issue - how does this work with the different agents, if one has the parameter defined and another doesn't?