I'm switching my hair to different hairs but the old one stays there even though it isn't on the layers.

it's just a visual bug. save the outfit you're working on and refresh the page, then reload that outfit and the extra hair will be gone. if you're switching salon hairs, it's best to remove the old one before adding the new one, unless you plan on wearing multiple at once.

the show/hide button is also bugged for salon hairs, with only the most recently added hair being toggled no matter which hair you're clicking the button on. unfortunately all of this makes it annoying to compare different hairs since you can't just toggle between them

Thank you, I was struggling with that.