Hi Michael :-)

I am getting the hang of it! I did it in MOI only! :-) But it is not fillet-able in MOI.

This time I made the whole Object in MOI then exported it as STEM and then imported the whole model in 123Ddesign. it was a bit hard to select edges I wanted to fillet but I can say it is doable! :-)

Edit: And if you want to see the filleted version it is here (I might have missed some edges) :

https://filesend.io/bb7704265296e30e71f1af2ed7fa3bd3/Original_MOI_Piece_Filleted_in_123D.3dm