Hi dean, well if you want to make the hole larger you can just use a larger cutting object. If you want to make it smaller you can fill it in using untrim or boolean union and then redo the cut. Or on a simple shape like you have here just build a new one.

If making changes like this is something you need to do frequently then you might be better off with a parametric history based CAD program, there are a lot out there like SolidWorks, Alibre, OnShape, Solid Edge, etc...

MoI is not really intended to be a complete replacement for those types of programs, it's focused on other qualities like being easier to use and to have a more fluid drawing environment.

- Michael