Hi Ben,
It is definitely possible to use different type of lines but this will require some Plotly knowledge (The library behind the Charts widget)
You can find documentation on how to tune your chart here: https://docs.mendix.com/howto7/extensibility/charts-advanced-tuning
Here you can find examples from line charts with different type of lines: https://plot.ly/javascript/line-charts/
Hope this will help!