Thanks. That does work. If it’s the only method that works, I may have to do it that way.
If I add the KerningGreek feature to the Latin Script, the Greek text is kerned twice as it is in your screen shot.
However, if I delete the adjustment pairs for Greek from the Latin Kerning table, the Preview text is kerned correctly when the script is set to Latin. Testing in Vivaldi and Firefox, only the Latin text is kerned.
This is too complex for my brain at the moment, it is time for a nap.