This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
You can add a source folder matching "Ignored Folders Pattern" (for example "test" with the default pattern "^(nbproject|build|test|tests)$"): the folder appears in the project tree, but it will disappear when NetBeans restarts. It might be clearer to give a warning.