I've been meaning to suggest this for months, but the previous improvements have already made Layers so nice to work with that I just got lazy about this.
But there's a few things I think could still be improved. And personally, I would prioritize the first one below, if I had to pick one.
I haven't been following DR's development, so I don't know if any of this is already done and ready for the next release. But in case it's not, here goes.
1- it would be nice to be able to right-click a layer in the Layers panel, and have all the options to add to layer and move to layer and remove from layer, right there. This would make it much easier and quicker to manage layers. And, I personally keep adding prefixes to layer names, so that they're sorted in the list below, so I can find them easier, because the list gets big and confusing. This improvement would remove the need to do that. It would even remove the need for using this list, I think.
2- It would also be nice to add a new layer directly as child of another layer, just by right-clicking the intended parent layer. Currently, you have to click the New button at the bottom, and then manually drag the layer to its intended parent.
Or when clicking New, the new layer could be created as child of the selected one.
3- I've suggested this one before, but I don't know if it's doable or not. It's harder to explain and I think the benefits aren't very obvious. It would be nice to override the visibility of objects that are contained in multiple layers, by toggling one of those layers on/off. So the layer you toggle, overrides their visibility. So regardless of whether its objects are visible or not, hiding this layer, would hide all of its objects, and vice versa.
This can be useful when you have certain objects in their respective layers, but then you'd like to have also have a way to toggle all of them on/off at a single click. And with this improvement you could add them to a separate layer, and then just use that layer to override their visibility whenever you needed. For example, to get the ceilings of a whole bunch of rooms out of the way all at once, so you could have a clear view of the rooms while you put in furniture or path nodes or something.
Currently, objects are always visible if any of the layers that contain them is visible, so this kind of thing can't be done. (And to be honest, because of that, currently it seems to me that there's no point having objects in multiple layers.)
This is also useful for grouping things for easy group-selections. Arguably, you can also use selection sets for that, but the way you create and delete them makes them more suitable for quick and dirty one-time grouping, rather than something a little more indefinite. The two approaches have different levels of control, which makes them appropriate for different use cases.