It turns out that I was wrong. The core rulebook does define a Coordinate System for dimensional addresses on pg. 117. In essence, the technicians divide space and dimensional planes into imaginary trays, and then divide the trays into little boxes. Each box is designated a code for location reference. To provide a reference point, our Earth is called 0-0-0-0. The first digit represents the dimension (or quantum level, from my previous attempt to fake something). The second, third and fourth components represent the X, Y and Z components of a three-dimensional notation. The orientation of this "map" is based on a navigation beacon formed from what is believed to be a subspace communication system found in the original Sherman Ring.
With that in mind, the worlds I've mentioned previously need new coordinates, of course. Here's the basic list, re-imagined:
Leninmir, lka Earth ((-3)-(-9)-17-(-13))
Thoth, lka Geb ((-3)-(-13)-(-19)-12)
Verne, lka Earth (0-18-13-12)
Part of the motivation in changing the values above is to make it easier for me to map to a two-dimensional representation of the gate map I'm creating, what the core rulebook refers to as a Guide Marker. The final map should be simple but sufficient for my gaming purposes.