Visited yesterday without charging.
There are exterior and interior parking spaces. The charger is in the interior parking.
It was a Friday holiday so it's hard to draw definitive conclusions, but as there is no physical gate at all it seems like the parking lot is accessible 24/7 even when the shop is closed.
The light and music was working. Maybe those are turned off in the evening and Sunday.
There's a staircase and elevator leading directly outside to leave the parking.
There are no payment instructions, it seems to be free. There's also no posted time limit, either for the regular parking or charging. But the chargers have the same overstay fee after 6h when charging with Swisscharge.
Right as I was leaving someone else entered the underground parking with an electric car to use the charger.