I am using CTA3 to produce a series of cartoon stills for educational use.  I need to be able to add keyframes that do not automatically interpolate from one keyframe to the next.  I know I can change the transition curve on a keyframe to "step" and it prevents this.  But I feel like there's a way to disable the interpolations altogether -- I think it is a setting that I've seen before, but now I can't find it.  Essentially, I'm trying to make the "step" transition be the default transition.  Is there a way to do this?

This interpolations are not an issue for me until I realize that I need to add a new still in between existing stills -- then I wind up with characters in intermediate poses that I have to deal with somehow.  Hopefully someone knows how to do this.  Thanks.