What do you think of adding a "Verified" tag? Probably just a comment in the "Leader" column, since there is room there and it is a comment column only.
To achieve the "Verified" tag the participant would need to have documentation of each visit - photo, TeslaFi, tracker, or something else. I suggest giving the tag to anyone who agrees to keep documentation going forward, since it is a new rule.
I have not kept documentation, though I do sometimes take photos. It really would not be that hard to snap a phone photo at each supercharger, or get a tracker. I don't think missing a couple in your tracker would disqualify the visits or the "verified" tag - like if TeslaFi did not record it for some reason, or you forgot to take a photo.