Hello,
To be honest, today, I am pretty sure that it is not possible in Vuforia Studio with the Time Series Chart Widget.
Y-axis field is not a multiple select item Widget.
More details in PTC Help Center on Time Series Chart Widget here :
http://support.ptc.com/help/vuforia/studio/en/#page/Studio_Help_Center%2FWidgetTimeSeriesChart.html%23
By the way, the 3rd library (ChartJS) used to display these charts seems be able to do that.
More details here in documentation of ChartJS :
https://www.chartjs.org/docs/latest/axes/
We can read :
Multiple X & Y axes are supported.
So, I thing here, we have a limitation of the implementation of ChartJS in Time Series Chart Widget in Vuforia Studio.
Maybe it is possible to create a custom Javascript function and a TML Widget as a workaround to display the Chart expected with multiple X or/and Y axis.
To be honest, I didn't check that.
At the end, I think that it is a good enhancement in a future release of Vuforia Studio.
It seems possible to improve the Time Series Chart Widget.
Best regards,
Samuel