Novice question: debugging a package fix: can I locally override just a single line of a long multi-line string in a package?

Trying to impact my real/working laptop as little as possible. Isolate my hypothesis of this is how to fix the bug” to some ephemeral configs/changes that won’t stick around. So the build-vm or test options I found seem to be what I’d intended.

Got it, thanks. Seems there’s a lot of flexibility, but that means lots of nix architecture I need to learn to grok my options better. I’ll start with jtojnar’s two ideas and see what happens.