The Move to Top button in your Queued Posts tab is to let your post move to the top of your first post for that social profile.
Let's suppose you have scheduled 4 posts for your Twitter profile and 4 posts for your Facebook page. Now, you want the Facebook page's post to be moved to the top. So, clicking on the Move to Top button will move this post to the top of your scheduled posts for your Facebook Page and not to the Top of your Queue.
This is how the Move to Top button works in your Queued Posts.