In the Mixed Reality Shell, there is a voice command to remove the hand ray visualization, it is "Hide Hand Rays" and "Show Hand Rays".

There doesn't appear to be a similar command for remote assist. Several of our training sessions with clients who are deploying remote assist resulted in a request for this capability. Some users find the hand rays distracting if they are always on and would rather have the ability to toggle them on and off as needed. Most of them navigate remote assist using voice commands and near interactions only.