Do you Mastercam guys have anything like Onecnc's NC manager, a process control utility that helps you break down a multi-tool program, so you can modify your machining parameters "after the fact" so to speak, and repost the new code?

Yes we do from simple 2d all the way 5-axis thanks god.
Makes my life much easer,I needed it today when making some changes to some 5-axis programs I ran today.

It's very easy to use and you can reorder the applied maching also. It's a tree of all the maching process being done. I'm going back 3 yrs since I use MC. I hated it at first THAN grew to love it. I come from using ENroute.

I find that for the bulk of my repeat jobs I can uptate my MC9 file to match shopfloor edits fairly easily. Change a parameter here or there change a tool regen, repost done!

With a solid post and decent programming habits, keeping the MC9 up to date is realistic.