Visited on May 19 without charging.
I missed the turn off Rietbachstrasse on the first try because I wasn't sure if it was the correct place. There are no arrows in the street, but there is a big totem with all the businesses for "Rietbachstrasse 10-14" and the Migros name is at the top.
There is an outdoor and indoor parking. The chargers are indoor. All parkings have no gate but a parking meter. The underground area closes with the store.
I had difficulty paying my parking with Twint because I had no cell connectivity in the underground parking. This would probably also cause some issues with the ad-hoc QR codes for charging, but perhaps the connectivity was better on that side, I didn't try.