How to add 12H format and 24H format in a Single Digital watchface

I guess, switch is the phone settings, which are automatically applied to watch too.
I cant verify it, do not have wear OS watch.

I thought so, there is no way to make a button that switches between the two?

I am not sure. This is one of the notorious questions, but I do not see a way with current state of things. We asked for a user defined tags/variables, but in times of GWS the request was declined with excuse, that GWS was meant to be for designers, not developers. On other hand, such feature would make the WFS extremely powerful.

I see, well switching the system format did change on the watch also.
Thanks for your insight.