Go to Sub watchface

Button : go to Sub. watch face

how do I make a button that subsequently shows another home-designed watch face ( designet in Watch Face Studio)

I doubt this would be possible without integrating interactive variables into some new version of the WFS. And I doubt they would do such in near future, because it could harm business model of some third party watchface creating apps.
I asked for such feature maybe 4 or 5 years ago. The excuse will be again “WFS was not meant for developers, but for designers”.
But who knows, maybe in wear OS it could be possible, if you could find the app id of other installed watchface app.