Yes, what dop suggested is more like what I'll probably go for a "ready to use X number of Layers".
It should do the job.
My current code is based on controlling the Z-Order of the current layer, Basically: one layer of instances have 3 the default Z-Order: Top, Mid, Bottom I'm not using all the manual numbers for unlimited Z-Order since it also change their scale based on the camera), so what I may do is each layer + default 3 Z-Order (Top, Mid, Bottom).
So 1 layer basically is not enough once there are plenty of other objects, (I just tried it, it's a mess) so I want to give the user some extra layers to have more control this is why I think I should add layers for the created instances.
I'm didn't decide how to approach the control of each instance specifically yet because currently if the mouse cursor is OVER an instance, it picks the top one and using SCROLL DOWN I sent it down on the Z-Order of the current layer, SCROLL UP sent it to TOP... moving them to other layers I should also let the user KNOW on which layer it is, so I'll probably need to design a "VISUAL" layer icons, that was my original idea but please share your thoughts.
I'm not sure if I can make it or not, because it could be complex for my level but I'll try to play with it soon and see for myself, I'm very hyped to try it already... I hope it's not too complicated.
One thing is sure, I ALWAYS naming my Layers, I never use the numbers... so I can follow them on the code easily (and I already have plenty of layers for the core software).