Since the wave release 1 2024 the behavior for selecting a queue in a consult action has changed and is not very user friendly.
When selecting the consult action a default queue is being set in the dropdown with queues. As the field is a searchable field it filters the list of available queues based on that value. This means that when an agent want to consult on another queue and clicks (logically) on the field dropdown only the already selected queue is visible. As such it seems like not other queues can be consulted.
The only way at that point is to clear all the text in the field to see the full list of queues which is not very user friendly. All others fields (eg. when search a team user in the consult action) allow you to use an "X"-icon to clear the field and search for something. I would think the same behavior should be at least in place for the queue field. Or even better that when using the dropdown always all queues are available for selection.