It’s not obvious to me how to delete credit card information that the tipping system automatically saves to the payment processor’s servers. I have two cards saved and I need to delete one of them as it is now obsolete.
I feel your pain, this is an issue.
The card handling UIs are currently being rewritten to work with newer APIs by Stripe. We don’t store any sensitive card details, everything is handled by Stripe. They have updated their UI libraries and we will update ours to work with them in the next beta release of Slipmat. This will happen approximately in a couple of weeks time, after that this should be fixed 
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