You might find it useful to compare the LXX of OT passages with the quotations given in Greek NT text, but it's not immediately obvious that you can do it in Logos. But it's possible, as the picture below shows (which compares the LXX with NA28) so let me show you how:
The resource I'm using is Old Testament Quotes in the New Testament, but this works equally well with Old Testament Quotations and Allusions in the New Testament. Like all harmony resources, you can specify which Bible version you want to use. The problem is that Logos doesn't let you specify two different versions.
The 'trick' is that if the version you specify doesn't cover a particular passage, that passage will be shown in your default Bible. So if you choose the LXX, all you need to do is change your default Bible to NA27/28, and you'll get the result shown above. Of course, you probably don't want to change your default Bible all the time, so use advanced prioritisation to ensure that your highly prioritised NA27/28 only applies to this one resource. (The prioritisation also needs to be above your ordinary prioritisations.)
