@Override
		protected boolean isValidChar( char ch ) {
			return super.isValidChar( ch ) || ch == '.' || ch == '$' || ch == '@';
		}
A completion provider for references within values. Only keys defined
in current properties file and in base properties files are used.
flatlaf-theme-editor/src/main/java/com/formdev/flatlaf/themeeditor/FlatCompletionProvider.java