When working in the input screen with the 3-d graphic in a frame to the right - any idea how to prevent the image from resetting every time a restraint is defined or redefined? I zoom in on the area I'm working in but when I change something, often the image resets by zooming out to the full extents. I checked the configuration file but none of the choices in the drop down bozes look appropriate.

You have two choices here:

a) Pull down the "Environment" menu and toggle the setting of "Reset View on Refresh".

or

b) Save the input, close the input, then reopen the input.

The behavior of the "reset view" is different based on whether the model is new or not.