Agario should have this new layer "Favorites" (pretty much self explanatory), you can left click on a skin and click "add to favorites" to add skins here. Its really annoying going through
Agario Skin png images | PNGWing
Skulls of Agario | Agar.io Wiki | Fandom
Agario custom skins | www.agario-skins.top
Agario-skins.net
All the Agario mystery skins - Page 3 | www.agario-skins.top