If you’re using .Wav files, why not put the backing vocals into those? Saves tying your hand up inputting a chord for the VH that probably needs to be doing something else…

And, if you are getting your .Wav backing from one of the audio backing/karaoke sites, those have proper harmonies already recorded, not just block harmonies derived from your singing. Hate to say it, but most great harmony backing vocals don’t track around like the Andrews Sisters! There’s more ‘call and response’ or contrary motion than block stuff.