There is a defect in the "New Transaction Trace" dialog in the Workstation. The problem seems to occur only when the Workstation is launched via Webstart. EM Version: 10.7.0.358 (SAP OEM).
The dialog is coming up, but in the filter criteria it is not possible to select "URL" instead of "User ID" in the combo box." The same problem does not occur for the explicitly installed workstation. As per the screenshots below it is possible to choose "URL" instead of "User ID" when using the webview but when using the "New Transaction Trace Session" dialog in the Workstation it is possible only to see the list of available options without the possibility to choose one of them.
EM Version: 10.7.0.358 (SAP OEM).
Make sure to use the SAP OEM version of the EM installer. Behavior may be different for the standard CA installer.
starting from Java later than 1.8.0_281
This is related to JVM access implementation related to a change in JVM swing application functionality in recent versions and not in code/functionality. The standard workstation installed from the same EM SAP build is working fine without any issues.
It is working on another system with Java "1.8.0_281" and the transaction trace window working without any issue.
It is also working on the same machine with version 1.8.0_201.
Not working in Java 1.8.0_321
This issue was happening due to JDK changes on how parent/child windows in the java applications are handled. In this case, when the user clicks on dropdown it is causing java security exception java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege. As of Java8 webstart support was deprecated and removed completely after java 9. The latest version of Java 9 also issue persists. This is not a product bug but Java-related issue so it can not be fixed easily without changing the product architecture.
It was not possible to find any java9 version which is working without any issue. The web start workstation support is deprecated since java8 and you can use the 1.8 version 201 update. Alternatively, please use the standalone workstation which is working fine with all the java versions
It has been tested up to 1.8.0_281 in our environment. It got broken after that and was not fixed as the webstart feature is deprecated. Our recommendation is to use a standalone workstation which is more stable and fast.
The following KB can also be useful when troubleshooting other similar issues in general:
Workstation Management Module Editor does not show existing management modules