How do I add Air Pod Pro to the battery widget?

It’s automatic. No one could manually add an AirPods Pro or model to the Battery widget, it comes up with it detects it. Also you might not even see it at times if you have a lot accessories display on it.

for example, in my case, at times I might not see the case charging... because I have the AirPods displayed and beats flex headsets... at Max it shows only 4 devices at a time.

to reiterate, it’s automatic.

You’re most welcomed.