Creating second Oracle database on ASM disk

I am attempting to create a second TEST database on an existing system that uses ASM.   All documentation and examples I have seen on Oracle's Docs state that one should create the datafiles on a second DiskGroup.   However, I want to create a second set of small datafiles for testing on the current production Disk Group while using a subdirectory to contain the files.   I am using DBCA to create the location for the Database area for Oracle Managed Files.   Looking at the parameter for the db_create_file_dest, I see the Disk Group name but no indication if a subdirectory will