Hello,
On 22.7 release was fixed ticket Failed to Set Titles for Axes of a Waterfall Chart. I tried to apply this update and found another kind of issue - I tried to apply some styles(font height and font bold) to the axis title and have no result.
Example:
var pres = new Presentation();
var chart = pres.Slides[0].Slide.Shapes.AddChart(ChartType.Waterfall, 0, 0, 700, 300);
chart.Axes.HorizontalAxis.HasTitle = true;
chart.Axes.HorizontalAxis.Title.AddTextFrameForOverriding("Horizontal Axis");
chart.Axes.HorizontalAxis.Title.TextFormat.PortionFormat.FontHeight = 8;
chart.Axes.HorizontalAxis.Title.TextFormat.PortionFormat.FontBold = NullableBool.True;
chart.Axes.VerticalAxis.HasTitle = true;
chart.Axes.VerticalAxis.Title.AddTextFrameForOverriding("Vertical Axis");
chart.Axes.VerticalAxis.Title.TextFormat.PortionFormat.FontHeight = 8;
chart.Axes.VerticalAxis.Title.TextFormat.PortionFormat.FontBold = NullableBool.True;
Result: Waterfall_test.zip (46.7 KB)