Behold! The Adobe Photoshop 2020 workspace!
It's got a lot of stuff in it which you may or may not be familiar with, but right now let me direct your attention to the "Layers" tab, which occupies the bottom right corner.
Each layer in a PSD is something like a transparent animation cel - wherever the layer has negative space you can see through to the layers underneath. Layers can be edited and manipulated independent of each other, and, important for our purposes here, turned on and off at will.
Visible layers have the little eye icon next to them. In the first pic here the layers from "sig" downward are the different parts of the basic nude Miyuki image.
Now each outfit has a couple of layers - lines, colors, and shadows at the very least but potentially a bunch more. This can really make a mess of the Layers tab, so it's a good idea to organize them in layer groups. As you can see here, each outfit has it's layers grouped together - the layer groups have that folder icon instead of showing a tiny preview image. In the first pic only the basic bunny costume layer group is currently visible, so she's wearing the basic bunny.
All the layers in a group can be turned on and off together, so it's very easy to switch around between them. As you can see in the second pic, I've got a couple different groups active, and she's wearing a couple different outfits all at once.
Of course, the layers within a group can be turned on and off individually as well. So as you see in pic #3, I've gone into the gothbunny and turned off most of the clothing layers, leaving only the goth skintone and stocking layers for Naked Goth Ninjabunny(!)
(If you noticed and were wondering, the menu icons for the pressure sensitive brushes all default to basic when I turn my tablet off. Doesn't matter, it says what they are underneath each one).