In the skin menu (Host > Skins) at the bottom there is a so -called Skin Designer, where you choose a skin from a dropdown, then a matching container, a file and finally some token with a setting and a value. As even the MinimalExtropy skin does not include an example for that, I would like to ask if someone could explain the Skin Designer and how to create skins that work with the skin designer (e.g. where in my skin to integrate these Tokens etc.)

The skin designer can be used to change an existing skin.

AFAIK, you can only change the attributes of Skin objects that are aleady in an existing skin.

So skin modifier would be a better name in it's current state IMO.