From the WordPress development reference, the add_action function requires two parameters with an optional two.
The first parameter, $tag is a string that is the name of the action to which the $function_to_add is hooked.
The second parameter, $function_to_add is a callable that the WordPress developer reference states is “the name of the function you wish to be called.” In actuality, it can be any callable: string corresponding to a function, an array corresponding to a static method, an array corresponding to an object method, or a closure.
The third ( optional ) parameter, $priority, is used to specify the order in which the functions associated with a particular action are executed. Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
The fourth ( optional ) parameter, $accepted_args is the number of arguments the function accepts.
Is there a better shortcut? Such as for example removing the characters function() if possible?
So no. There is no shortcut at all. Passing a closure may require a few less characters, but is not a shortcut. And as explained in the comments, using a closure (anonymous function) as the callback is not recommended because it does not allow for an easy way to remove the action.