I have created this chart in Excel, but want to add another line to the secondary axis - I cannot see a way of doing this in Create Custom Combo Chart which seems to accept a maximum of 3 data series, and does not display the fourth data series that is in my table.
Forget creating the chart as a combo first thing. No flexibility.
Make a column chart with all of your data (all 3 or 4 or 15 series, whatever).
Select any series, right click, and choose Change Series Chart Type from the pop up menu.
Now you can individually change the chart type and axis of any and all series in the chart, in any order, independently of each other.
I think Jon Peltier's reply answers the question well, I would add the following information.
When you add the Series 4 or other data for more series, please select the chart > Insert tab > Recommended Charts in Chart group > All Charts tab > Combo, check the series, and choose the chart type, whether use secondary axis for them.
