I’ve been gathering more materials. The medieval Greek commentaries on the bible (catenae) are made up solely of chunks of quotations from earlier authors. The catena published by John Cramer is particularly good for material by Eusebius, and has a nice index at the back of which pages to look at, unlike another catena by Possinius that I had to leaf through. I obtained photocopies of the Eusebius pages of the volume on Luke/John. Using the TLG, I found that many of these quotations do indeed turn out to be from the “Quaestiones”; some look as if they might be new fragments.
It’s interesting that so many catenae do exist in publication, and all in very old editions. Cramer, being 19th century, is the most modern of them. I can’t help feeling that someone should translate Cramer. It could not fail to be interesting.