this is remix of that work.
https://www.thingiverse.com/thing:3249319

'Marlin' is firmware which you can intall to the machine.
I recommend XLoader for Windows users to install.that's so easy!
now I modified v1.4.6 for MEGA-S and named as 'v1.4.6s'.
of course, s means MEGA-S.
(not to say it includes the I3 Mega with upgrade kit)

the different point from v1.4.6 are...
1)all default values has fitted for MEGA-S
so you don't need to send command line 'M92 E384' or 'M203 E30'.
2)the file list on SDCARD is displayed correctly
everything appears natural. I fixed bugs in sorting.
3)'Special Menu' in print menu changed to 'Marlin'
'change' means not only rename but also re-build menu items.
especially in the mesh bed leveling I made a lot of changes.
4)startup chime is back!
I have been miss that chime. so made it a original style.

NOTE: if you changed the stepper motor drivers,this will not work.
motor drivers=TMC2208 and with reversed connection
as far I know, old I3 Mega and S has that drivers.

2020/6/4 changed DEFAULT_ACCELERATION 1500 -> 1000.