I did give it a bit of a non-detailed response because I didn’t know how much assistance you would need. If you get stuck somewhere just ask, I’d be happy to help. There is quite a few pitfalls that one could fall into but writing a book every time a bespoke keymap question comes up is best to be avoided. That being said in this case it should be fairly straight forward unless you pick the wrong key. Not knowing exactly what device you programed into myharmony I think I could only suggest to make sure what you use comes up with a valid key id as I outline in my (largely not applicable to universal remotes) OSMC remote guide [here].