This is really inconsistent - I’ve used this feature several times (on this hull, no less) and now it’s stopped working for new designs.
Selecting the base layer and hitting ‘toggle hidden’ is now dropping the z-level and recoloring it to white, but it’s not otherwise hiding.
Looking inside the craft file, I see this:
F4_Gunship1,255,255,255,255,0.000000,0.103200,0.000000,0.793600,1.000000,0,0
F4_Gunship1,219,254,200,255,0.000000,0.103200,0.000000,0.793600,1.000000,0,0,COLOR2,255.0000,255.0000,255.0000,255.0000,COLOR3,255.0000,255.0000,255.0000,255.0000,HIDDEN,1.0000,0.0000,0.0000,0.0000It looks like the layer got expressed twice. I can delete it through the text file, but I have no idea how it got stuck there. Old existing designs are fine. This is happening for any new ship that I start from scratch, selecting from the hull picker.