Big Thanks. Rated 5 out of 5 stars
Much Thanks to Dagger (developer) for fast reply here and double Thanks for Dagger's steadfast attention.
I have nothing against black backgrounds but I mostly end up removing them for stand-alone viewing and editing, when necessary.
Meantime, Much Appreciation to steeviebops for that (obvious) remedy. Should have tried that first. Dagger will hopefully develop a suitable fix. Meantime, I'll just apply your solution.
Again, very grateful to both.