Nope as its not designed to work like that. The Battery widget will only show the device its on and anything connected to it like Watch, AirPods or bluetooth devices that report their battery level back.Isn't there any way to get my iPad Pro on my widget on my iPhone? I use my iPad quite a lot for work and would help a lot in the evening to glance and see if it needs overnight charging
You can check your iPad battery level via the Find My app and checking the location of your iPad as it shows the battery level as well.