private VisualElement CreateTopBar()
        {
            var bar = new Row().WithName("top-bar");

            var buttonsColumn = new VisualElement().WithName("top-bar-button-column");
            {
                var loadButton = Create_Top_Bar_Button(LoadVisualTree).WithText("Load");
                var saveButton = Create_Top_Bar_Button(SaveVisualTreeAsset).WithText("Save");

                buttonsColumn.ADD(saveButton, loadButton);
            }

            var spacer = new VisualElement {
                name = "top-bar-spacer"
            };

            var fieldsColumn = new Column();

            {
                uxmlField = Create_Top_Bar_Field <VisualTreeAsset>();

                ussField = Create_Top_Bar_Field <StyleSheet>();

                fieldsColumn.ADD(uxmlField, ussField);
            }

            return(bar.WithChildren(buttonsColumn, fieldsColumn));
        }