Hi Andrei,

> So is it possible to change defoult primary axis to Y?

There is no way to alter the orientation picker itself, but like Max shows above you can change the labeling of axis directions in MoI to something else other than the default standard system, that's under Options > View > Axis labels. That will change the displayed labels for x, y, z directions and also change x,y,z coordinate input to be interpreted as those directions as well.


> Also whanted to ask why MOI is Z-Up orientation?

Well, it's the standard way that engineering designs have used for many centuries now... When you lay down a blueprint on a flat table top, that's the "plan" view, with x and y axis directions mapping to the tabletop, with the added z direction mapping to height above the table.

If you prefer the "left handed" type system that is more oriented around a vertical computer screen as the base position, set your axis labels option as Max shows above.

Generally things that are oriented around any kind of physical construction use the z-up system since that's been the standard way for a long long time greatly predating computer systems.

- Michael