How do I create a gizmo?

Hi! First post here. :)

I'm working on a plugin using MAXScript that will take a set of models and build a new model by placing and bending copies along a spline.

What I'm currently trying to do is to create a gizmo to show and set where a model will connect to the next. I just can't find any info on how to create a gizmo.
Is there any "createGizmo"-stuff or is it just an invisible simpleObject that is connected to the values in another object?
Just to be clear, by gizmo I mean one of those (usually) orange models that shows up when you're using modifiers like bend, mirror and the different kinds of FFD.

Oh and while I'm at it I might as well ask...
At the moment I have made a simpleObject SegmentSet that stores a list of the models to use and information on how they are to be connected to each other.
Is this a good approach?
I am aiming for something like the Rigid Body Collection, preferably with an icon in viewport that always have the same size, regardless of distance. At the moment I just have a triangular mesh that represents the SegmentSet.

Grateful for any help. :)