Alerts evolve over time and it becomes a chain of behaviors. The foot tap is very useful and you can eventually elongate that into repeated foot touches. Barking is great too- and this can come with time.
One of the more useful alerts in truffle hunting in addition to the ones you mentioned is a nose targeting behavior. Truffles can be hard to see in the soil, and feet touches while excellent can either (if aggressive) damage truffles (not that big a deal in wild settings), or be not as precise depending on the dog. Nose touches are direct on target. That’s why we encourage students when possible to explore the nose touch. When you have dug out a small hole and you still can’t see the truffle, Mika can then go in and touch it with her nose… “oh THERE it is” you’ll say. Also comes in handy for that backing up maneuver you actually did.
Dogs when locating later in the field will often put their nose right on the truffle. We tell students to always “watch the nose!” If you have this as part of your behavior chain the behavior is much more noticeable and clear and easy to identify. What you are doing now looks really good though. It will evolve.
As for the tail, it depends. Some dogs do it, some do not. Some VERY much so and have helicopter tails. Just start paying attention to it if you can because it can be an indicator of shift in odor or if she is on source. You’ll notice it likely on video play-back more.