For example I need to draw someting on CanvasItem, scale it or anything and then draw it on another CanvasItem.
But there is no way to get texture from CanvasItem, so I can't just get it from it and draw on another.
What kind of CanvasItems are you working with? I don't think you generally use that class directly, but rather use something that inherits from it (like Sprite)
Well I need to draw something dynamically on a texture and then draw this texture on some element. So I suppose I need to create a Texture and assign it to some CanvasItem to draw?