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We can observe many instances where in early Jedi training, an initiate learns telepathy by moving objects with their mind. This demonstrates that hand gestures aren't necessary to using the Force to manipulate the world around them. It does, however, require mental concentration.
When I was training in archery in the past, my instructor taught me that the sport focuses on mental concentration. For optimal performance, there should be no unnecessary physical movements as that will consciously and subconsciously distract the mind. Given the way the Force works, I assume it shouldn't be too different.
So that begs the question: are hand gestures necessary in any way? Given we've only seen fundamental powers being hands-free, are they required for only more advanced Force powers?
Out-of-universe, it is necessary to visualise the use of Force powers to the audience, but how are they justified as necessary movements in-universe?