Setting Custom Properties on project level through JUnit

You could save the project after run

https://www.soapui.org/apidocs/com/eviware/soapui/tools/SoapUITestCaseRunner.html#setSaveAfterRun(boolean)

like the command-line argument

-S: Commands the runner to save the test project after the test run finishes. Use this command-line argument if you store data within the project during the test.

https://support.smartbear.com/readyapi/docs/soapui/running/automating/cli.html