I think there might be a bug in the 3dmax exporter. The "babylon properties" option disappears permanently and gets rewritten as "file exporter" whenever I make my own workspace. To check this, I reinstalled the plugin and the "babylonjs properties" option was showing in the default workspace (as it should). I created a non default workspace and the "properties" option disappeared and changed to "file export" again. The option was irredeemable until the plugin was reinstalled.