Yes, there is a way to format a chart in Excel to properly represent an outlier data point without having to make the axis long enough to include the whole bar. One way to do this is by using a combination chart, which allows you to display different types of data on the same chart.

Here are the steps to create a combination chart with a zigzag bar for the outlier data point:

1. Select the data range for your chart, including the outlier data point.
2. Click on the Insert tab in the ribbon and select the Combo chart option.
3. In the Combo chart dialog box, select the Clustered Column chart type for the first data series (the one with the low values) and the Line chart type for the second data series (the one with the outlier value).
4. Click on the OK button to create the chart.
5. Now you should have a chart with two data series, one represented by columns and the other by a line. The line represents the outlier data point.
6. To add the zigzag to the line, right-click on the line and select Format Data Series.
7. In the Format Data Series pane, go to the Line Style tab and select the Dash type.
8. In the Dash type options, select the pattern that looks like a zigzag.
9. Adjust the other formatting options as desired, such as line color and thickness.
10. Finally, adjust the axis scaling as needed to make the chart more readable. You can set a fixed minimum and maximum value for the axis, or use automatic scaling with a maximum value that is higher than the outlier value.

By using a combination chart with a zigzag line for the outlier data point, you can create a chart that properly represents all the data without sacrificing readability.