Hello,
Cerner does not allow passing input parameters and return them on your callback or token. You need to follow the standard HL7 SMART on FHIR workflow.
There is a mechanism, where we could add a custom param in our configuration, so that when your App is launched you would get back that configured param with its value in the token response. However, this is a not a recommended approach and has its own limitations.
Thanks,
Fenil