The problem is that when I add Submodel_31 into Submodel_3, Submodel_3 becomes a MPD file.
When I look back to the Main Model, the Submodel_3 I have there is the ldr file, not the mpd file (with Submodel_31), and when I try to add the Submodel_3.mpd (with Submodel_31), MLCAD doesn't allows me since I can only import .LDR files into a MPD file.
Did I make myself clear? What I want to say is that MLCAD only allows to import .LDR files into MPD files.
Thanks for your help