How show battery level

First you should check if your attribute is working. Click more details in the device popup. It will show all attributes.

Hi, yes in my case it is io8 - as per the attached screenshot.

I set it up as below:

And assgined to the device.
The attibute test returns the value of io8 but doesn't bring battery percentage status in the GUI.

But where's the battery level in the output?

Do you mean on this list?

no batteryLevel property on this page.

Then your computed attribute is not working.

Well, any way to make it work then?

Well, you need to figure out why it's not working. You're missing something. Are you sure you waited for new data? Are you sure those io values are not copied attributes?