While I ended up not having enough time to visit in September, I did some research about this location.
The website says says there are very few parking spots. It mentions 6 parking spots with charging stations at 0.40CHF/kWh https://www.lindt-home-of-chocolate.com/de/anfahrt/ There's a PDF with the opening hours and parking prices https://www.lindt-home-of-chocolate.com/wp-content/uploads/2023/09/230901_Parking_A4.pdf 30min=1CHF, 1h=2CHF, 2h=4CHF, 3h=6CHF, 4h=8CHF, 5h=12CHF, day=50CHF.
At the bottom of the document it says "Sollten Sie ausserhalb der Öffnungszeiten Zugang zum Parkhaus benötigen, nutzen Sie bitte dazu den Eingang zum Treppenhaus auf dem Schokoladenplatz sowie Ihr Parkticket zum Öffnen der Türe." so it might be possible to stay parked for longer than the actual opening hours.
On September 21st I drove around the building and confirmed there aren't any charging stations outside, all must be in the underground parking.
In the live data there are a lot more chargers than indicated on the website, 25 total at the moment. Based on the charger names and the Chargemap pictures, numbers 208 to 233 are probably the 6 always-public referenced on the website. Chargemap has more pictures, where we see 2 chargers behind spaces 264-267 with "Mieter" written on the ground and a sign on the wall "Reserviert International Montag-Freitag". I wonder if they meant "Internal", and those might be available on the weekend? This still leaves many of the chargers unaccounted for. It shouldn't be too difficult to clarify with a visit, since every charger has a parking space number and we just need to figure out which parking spaces are public and which are reserved.