For very good reasons other game engines allow you to select an instance on the layout via a list view.
This is very handy if the thing you're after is invisible. And its usually quicker in general anyway..
(think Hierarchy view in Unity, think "layer Property" window in Game Maker, Godot... blah blah - I think just about every game engine has one)
Don't know about you but I keep expecting the Layers window to be like a hierarchy view, little side arrows next to the layout name, you click on it and it expands a list of all the instances on that layout. Then you can click on it, drag it to another layer, copy it, edit its props... etc.
Am I missing something or does C3 not have a list of instances anywhere? (the debugger has a glorious one!)
That sounds like a good idea. I haven't needed for my game as I am generating instances on the fly
But I can imagine that if you have a large layout with lots of instances of a thing with varying instance variables then this would be very handy.
The list of instances could exist under the object itself in the project view and under the layout in project view with instance properties in the properties view.
I suppose you could manage your instances directly in layout but still.
There is a suggestions forum, chuck it in there, https://construct3.ideas.aha.io
It is good to have input from users of other engines. There are not so many here.