What exactly does this do?
what it primarily is good for in my opinion is that when you start max, your material editor is populated with this 24 slots of materials, depending on the preset you choose. and i want those to be corona materials, without having to convert them via the converter script.
because this information doesn´t get stored in the "maxstart.max" i can create but in some preferences "medit.mat" file loaded by the chosen ui preference, and buried away somewhere under user/appdata/local/autodesk/blablabla... the preset does that, among other things like defaults for "by layer" or "by object" and stuff like the default type of shadows for standard lights and so on...
vray eventually had that. like much else in 3dsmax it can quite mess up your max, but better to have it than not i guess.
because at the moment even if i choose corona now to be my primary renderer (and save this in the maxstart.max) those slots gets populated with vray materials at startup (because the default chosen before on my computer was max and vray) which then produce error messages of course.
edit: and of course, i could reset that either or edit the chosen preset like i did with an updated "medit.mat" file populated with 24 clean midgrey default corona materials. so if you know where to look you get there, but it´s hmm, awkward like so much else in 3dsmax. all this legacy and new stuff thrown together plus all those user configuration things are killing me. a serious pain!
cheers,
chris.