Click into the chart you want to add another KPI to.
Then click the 3 dots icon you see in the upper right hand corner of the detail screen and select “Add Data Series”.
A new column will appear where you see your list of months, click to select the KPI you want to add.
Pro-tip: Putting related KPIs into a single chart is a great way to clearly see relationships and trends.
Here is how to delete a KPI from a chart:
Click into the chart you want to delete a KPI from.
Then click the 3 dots icon you see in the column of the KPI you want to delete from the chart.
In the menu that appears, click on the "remove from chart" option you see at the bottom of the list.