You must modify the obj file. (with Notepad++/ ArtOfIllusion/ Blender).
Rename the moving part with new prefixes.
e.g. You have a door and hinge objects name;
rename hinge to hinge_1
and door to sweethome3d_opening_on_hinge_1_door
Save and import.
I will tray to do this directly from SH3D when I'll have some time to test.
At that moment I don't know other way.