Hi @gab1one,
thank you so much for your help! 
what would be the correct implementation of these dialogs?
(I could not find any easy to follow example
)
E.g. while using the Example NumberFormatter Node I would do the following:
NodeModel:
public class NumberFormatterNodeModel extends NodeModel {
protected NumberFormatterNodeModel() {
super(1, 1);
}
private static final String filePath = "filepath";
private final SettingsModelWriterFileChooser m_filePathSettings = createWriterFileChooserSettingsModel();
static SettingsModelWriterFileChooser createWriterFileChooserSettingsModel() {
return new SettingsModelWriterFileChooser(filePath, null, "File System Connection", FilterMode.FILE, FileOverwritePolicy.FAIL,
EnumSet.of(FileOverwritePolicy.FAIL, FileOverwritePolicy.OVERWRITE), new String[] { ".xlsx", ".xls", ".xlsm" });
}
Node Dialog:
public class NumberFormatterNodeDialog extends DefaultNodeSettingsPane {
protected NumberFormatterNodeDialog() {
super();
SettingsModelWriterFileChooser writerFileChooserModel = NumberFormatterNodeModel.createWriterFileChooserSettingsModel();
FlowVariableModel writeFlow =
createFlowVariableModel(writerFileChooserModel.getKeysForFSLocation(), FSLocationVariableType.INSTANCE);
addDialogComponent(new DialogComponentWriterFileChooser(writerFileChooserModel, "filewriter", writeFlow, FilterMode.FILE));
However I could not get the portsConfig / PortsConfiguration working in the SettingsModelWriterFileChooser (null seems not to be allowed) 
How would I set the ports config in the above example?
I looked into the POI Excel Writer Node - but could not figure out how to apply it to the basic NumberFormatter example