Not a new issue but I wonder if the editor needs to do so much work upfront when opening a Layer trait, as it seems to take longer the more images/layers the trait has. Once you are north of 20 images the delay is noticeable. Extreme examples can be found in Flying Colors where some of the pieces on the “VP” map include layers comprising up to 200 images - one of the takes about 18seconds to open on a fairly fast MacBook.
I checked in a profiler and almost all the time comes from calling
pack() on the dialog. Digging further into this would involve looking at how the layouts are interacting.