How should I credit a Pro Tools engineer on a recording??
If we can’t determine what the engineer used Pro Tools for, perhaps the safest thing is to use the “engineer” credit, which is generic.
If the recording already credits recording, production, mastering, and mixing to other people, we might suppose that the Pro Tools engineer was not the principal person responsible for those duties, but that still doesn’t lead us to anything definite.
I tend to use “edited by” for that (typically with a corresponding sub-optimal credits annotation).
With Pro Tools you can do much more than editing though. Really the general engineer relationship is the only fit here.