Well, that begins to drift into a marginally different area. I think a Sleight of Hand or Palming skill of some kind is a great idea. The ability to conceal small objects on one's person. It would synergize well with other skills, including gambling.
But within the confines of the gambling skill, I'm thinking more in terms of "knowing what you need to do to effectively influence the odds without getting caught." The wiki says skills should be as general as possible; there's my attempt at being general. Counting cards. Shaving dice. Nudging the table. Maybe some of those have a "physical execution" element which might better fall under a "Palming" skill or something.
I can totally see the ability to conceal small items developing separately from Gambling knowledge, but I can't see knowing how to cheat at a particular game developing separately from knowing the game. But like I said - that's just my take, and I can completely understand the opposing view.