No, the Creator Studio is only to upload and submit your items!
Everskies does not currently provide a built-in tool to create items, so it's all up to you to find a software that works for you. Many of our Creators use softwares as Procreate, Photoshop, Clip Studio, Krita, Sketchbook and so on. The most important thing is to remember our max canvas size, 221x340 pixels. You can find bases and canvas examples and explanations HERE.