Hi Jim,

> It would be nice to have a feature that would enable
> you to mark one ore more objects as visible, but NOT
> selectable. They would respond to snapping, but you
> couldn't select them at all.

That's what the "Lock" function does - to lock an object, select it and then click the Edit > Lock button here:



To unlock them later on, push that same button when you don't have anything selected and it will unlock all locked objects. There are also a few other options like holding down Ctrl to do an "unlock subset", and some options you can set for whether the locked objects should switch to a gray color or whether they should retain their normal color, see here for more details:
http://moi3d.com/2.0/docs/moi_command_reference4.htm#lock


But the purpose of locking is to make an object get semi out of the way by not being selectable but still remaining visible and snappable.


> Something that might also be useful is either a group
> "object" or layers, so you can organize your scene a
> little more.

In MoI there is a "Styles" function that you can use to organize objects by colored categories like layers, and also you can assign objects a name to turn them on and off using the scene browser. The scene browser is the spot to go for these kinds of organization methods - see here for more info:
http://moi3d.com/2.0/docs/moi_command_reference11.htm#scenebrowser

You open it by clicking on the "Browser" button at the bottom-right area of the main window:


- Michael