There are no entries in the alert selection dialog box/metric groupings selection dialog box for a management module. The dialog box is blank if trying to select alert or metric grouping.
The problem is related to the Management Module names. In the above scenario, there are multiple domains set up in the environment.
There is a Management Module with the same name and jar file in the <Em-Home>/config/modules directory
and also in the <Em-Home>/config/modules/mynewdomain subdirectory.
After renaming the Management Module in the Superdomain and restarting the EM, the problem is resolved.