Visited yesterday, charged with M-CHARGE RFID without any issue.
The chargers are in the underground parking. There are no gate, no payment and no maximum parking time posted. The only sign is that the parking closes 10 minutes after the store.
It's not clear how you are supposed to reach the entrance to the parking. If you arrive from the freeway, the roundabout map shows the third exit is forbidden to cars, but that's the only logical way to Migros. I drove further trying to find the official way in, but I ended up on another road that's also forbidden to cars. The actual sign at the roundabout exit contains more details, and I think it's specifically through-traffic that's forbidden. But there's no mention of Migros on the sign. It mentions the SBB bridge, but as a non-local I have no idea where that is in relation to the roundabout.