Sounds like an unusual part. In my view wizards are for common shapes, thinks like circles, slots, bolt circles etc. Other parts ought to be done with CAD and CAM tools. We could never do a wizard for every shape of part.
That said, there may be a way to do it. The wizards let you save the gcode step by step into one big file. Watch the video, it shows making a part with a couple circles and a bolt circle.
You could make each of your slots, defining the X,Y location as appropriate, then Post the code. Then return to the slot wizard and define the second slot, post that part, return, etc until you have made all the slots you want.
When you are done return to Mach and you will have one big Gcode file with all the individual slots in it. I realize this might be tedious, but it would work.