Is there documentation available? Or any default template to start with?
Note that this feature is still in soft launch (currently the idea is to make it available in the custom app creator framework so that it can be used in custom apps, instead of releasing it in the Dashboards app).
A button panel is a table visualization where each table row is displayed as a button. The protocol contains all the information (actions, type of button, styling, pages, etc).
There is internal documentation available, and some button panel protocols already exist and different buttons/panels have already been designed.