I'd say the main problem is this, though:
This instance should probably be on a layer with less instances, or on its own layer.
I'm only posting again because you've split the above posts from the other
thread, but it really was the same problem, from a 4 year old thread. The problem being the instance creation order can't be sorted, which has nothing to do with the amount of instances on a layer. Instances on a layer has no bearing on being able to move a newly placed instance to the top of the instance creation order list.
I have a room with 200-300 instances on various layers, and the instance creation order list does not cater for layers in any way. As you know, it's just a list of all instances in the room, and having to drag a newly added instance from the bottom to the top is the only method within the editor to arrange instance order. There needs to be at least 2 simple buttons just like the room manager now has, move to top and move to bottom. It would save huge amounts of time, and as I've asked above, why after 4 years of asking can we not get this basic feature, or at least a reason as to why it can't be done?
My theory is the people who can approve it have never had a room with hundreds/thousands of instances, and wanted to move an instance to the top of the list, because if they did, they would add it to the next beta asap.