I was hired as a shift from outside the company. I had worked in a coffee shop about 10 years prior, but no food service since. Here's my take: It is so difficult learning the barista basics, and then the shift supervisor stuff right away with very little absorption time. Now, I will say that I am moderately intelligent and learn quickly. However, there is a curve to all of this, and the balance of power is also learned on this curve. This shift may just be trying to find that balance, and having an issue doing so. It is very hard (or at least I found it difficult) to jump in the middle on my first few shifts and tell people that had been there much much longer than I had, who knew how everything worked and how to make everything, how the shift would play out (who was going to do what tasks, who was planted where, breaks, etc). I came in with an advantage I think - I have a degree in psychology and my focus in my degree had been learning, memory and behaviour, so I was able to find a way to ask about things to get them done, rather than tell people what to do, ("Hey, looks like we still need to get x, y, and z done, who would prefer to do what?") and it came more naturally.

In handling this new shift, perhaps a gentle approach of letting them know how you feel while they are working, and helping them improve. I.e.: during downtime "hey, I know you are still getting the hang of all the drinks, I know it took me a while. Is there anything that you have questions on or that you would like to go over? I would be happy to give you a hand." During peak, if you notice they are overwhelmed, or have planted themselves in a corner "Hey, would you mind if we switched places/double barred? There are a lot of drinks in line and we want to get this out efficiently. You are doing great, just let me help you out." The new shift is probably putting themselves there because they know that they are slow, but genuinely want the practice. Validating their effort, and offering to help them is much better in the long run to get to a smoother shift than simply getting upset with the situation.

As spagoogly said though, they have been hired to oversee the big picture. It is their job to put people into a position, and to oversee the day. It takes some shifts longer than others, and it is particularly difficult for an outside hire to find that balance. Offer to help them learn the dynamics, in a peaceful and respectful way, and they will probably pick up a lot quicker.