It would be great if the simulator could run at different speeds (half, double, frame-by-frame, etc.). This could help debug edge cases or speed the game up to get through a slow part.
I'm not sure what your toolchain looks like, but if you develop in Panic's own Nova editor, there's some pretty handy breakpoint and debugging tools that work nicely with the SDK. This would essentially allow you to go frame-by-frame, although it wouldn't really help if you're looking to "double" the speed.
For things like that, I've put temporary DEBUG flags in code before to automatically skip certain things if a global DEBUG variable is true.