To reproduce, run the example below und make sure that the parent of nested columns is not/only partly visible

- click button to scroll to parent of nested columns
- expected: parent column scrolled to leading edge of table
- actual: scrolled such that last column aligned with trailing edge, parent scrolled out to left

Culprit seems to be TableViewSkinBase.scrollHorizontally(targetColumn), in particular its code to calc the horizontal location of the target:

        // work out where this column header is, and it's width (start -> end)
        double start = 0;
        for (TC c : getVisibleLeafColumns()) {
            if (c.equals(col)) break;
            start += c.getWidth();
        }

if col is a parentColumn, the break condition is always false, thus scrolling through to the end.

The example:

    public class TableViewNestedScrollHorizontalBug extends Application {
    
        private Parent getContent() {
            TableView<Locale> table = new TableView<>(FXCollections.observableArrayList(
                    Locale.getAvailableLocales()));
            table.getSelectionModel().setCellSelectionEnabled(true);
            TableColumn<Locale, String> countryCode = new TableColumn<>("CountryCode");
            countryCode.setCellValueFactory(new PropertyValueFactory<>("country"));
            TableColumn<Locale, String> language = new TableColumn<>("Language");
            language.setCellValueFactory(new PropertyValueFactory<>("language"));
            TableColumn<Locale, String> variant = new TableColumn<>("Variant");
            variant.setCellValueFactory(new PropertyValueFactory<>("variant"));
            TableColumn<Locale, String> display = new TableColumn<>("DisplayName");
            display.setCellValueFactory(new PropertyValueFactory<>("displayLanguage"));
            TableColumn<Locale, String> nested = new TableColumn<>("Nested");
            nested.getColumns().addAll(countryCode, language);
            table.getColumns().addAll(display, nested, variant, new TableColumn<>("Dummy"));
    
            Button scrollTo = new Button("ScrollTo Nested");
            scrollTo.setOnAction(e -> table.scrollToColumn(nested));
            BorderPane pane = new BorderPane(table);
            pane.setBottom(scrollTo);
            return pane;
        }
    
        @Override
        public void start(Stage primaryStage) throws Exception {
            primaryStage.setScene(new Scene(getContent(), 200, 400));
            primaryStage.setTitle(FXUtils.version());
            primaryStage.show();
        }
        
        public static void main(String[] args) {
            launch(args);
        }
        
        @SuppressWarnings("unused")
        private static final Logger LOG = Logger
                .getLogger(TableViewNestedScrollHorizontalBug.class.getName());
    
    }