Is there any way to edit in more sophisticated way a watch face designed in Watch Face Studio?

It is built into Watch Face Studio
Click Add Component Ranged Text
in the right hand column for that Complication Settings → Default Provider
Watch Battery

In Beta 1.0 you see it in the Run Window, the video Tutorial shows it working correctly in the build window too so I assume it is coming there in a new version

The Video goes pretty fast but it shows a lot of useful information if you step through it.

Samsung Developer Relations