Remap modifer key (right option) to altgr?

How can I remap a modifier key (right option) to be the AltGr key.

I should add that I'm using a US keyboard layout on a Mac Book Pro so no physical AltGr.

I'm trying to do this so I can send the AltGr to a Windows virtual machine.

BTT can not do that, you’d need something that works on a lower level. Maybe it’s possible with the Karabiner app