If you want to examine how certain segments of a pie chart are evolving, you can easily create an interaction between your pie chart and a line chart.
To do this, you must first create your pie chart. Then, create a link with a new line chart via the "Customisation" tab of the settings panel.
This will automatically create the line chart in a new box.
In "preview" mode, or in the Dashboards application, simply click on the pie chart segment whose evolution you want to see: the line chart will be automatically updated.
Tip: only pie charts and line charts can be interdependent in this way. If you've already linked a pie chart to a line chart, you won't be able to change the line chart into another type of graph.