Hi! My CoreXY has the endstops mounted in the top left corner, and my Y axis was inverted. Now I switched the motorplugs on the RAMPS and my axes are ok now, but now the Y endstop is on my Y max position. It seems that Marlin does not support max endstops when in CoreXY Mode? Is there a software workariund or do I really have to move the Y endstop?
What you need is to look at homing direction in Marlin and set it to max instead of min. If memory serves that means setting the value to 1 instead of -1.
But in my experience the endstop should stay plugged in to the min port.
unfortunately that setting will be ignored if you use CoreXY kinematics 
I think I’ll just move the endstop.
Got it. I’ve only played with Cartesian so far.
For what it’s worth, homing to minimum usually works better anyways. My first printer had a y max endstop and it was a bit annoying and caused me some issues when I was first setting it up.
My corexy homes to X and Y max, but I had to change my homing routine to home one axis at a time, then back off the switch.
Try this instead of just G28 X0 X0
G28 X0 ; home X
G0 X5 ; back off X switch
G28 Y0 ; home Y
You need to move the endstop had the same issu myself. Mine printed in mirror first after i fixed that i had to move the endstop 