In LibreOffice 3.5.
- Create your chart as normal. I’ll assume you’ve created some kind of line graph.
- Right-click on the chart and select Edit.
- Right-click and Insert/Delete Axis.
- Select a secondary Y axis. Now you’ll have two Y axes but they’ll both use the same scale.
- Right-click the data series i.e. the line/plot of whichever plot you’d like to use for the new Y axis. If it’s obscured and you can’t click it, then right-click any other part of the graph, left-click to remove the menu, then tab through the elements of the chart until you get to the data series.
- Select Format Data Series.
- In the Options tab align the data series to the secondary Y axis.
- Your new Y axis should now have its scale changed to be appropriate for the data series it’s aligned with.
Reference: [Solved] In Chart need different left and right Y axis
