I’ve been working on an interactive map of the Tigray churches in Ethiopia since no such thing existed. It’s currently a work in progress but as far as I know it’s the most exhaustive map of the rock-hewn churches of the Tigray Region available. I’ve based it off your guidebook, the Lonely Planet guidebook, several maps and brochures I picked up in the region itself, and finally individuals’ online accounts of how they accessed certain churches.
The map is visible on on my blog here: https://new-faces-new-places.com/2017/11/11/tigray-churches-ultimate-confluence-of-culture-nature-history-and-adventure-ethiopia-travel-blog/
You can also look at it directly here: https://www.google.com/maps/d/viewer?mid=1VuasgrAHXoS1HN0Li1z2OAz0Xd4&ll=13.940869831926213%2C39.55033058858044&z=10
I plan on making it more accurate as time goes by, but for now I’ve distinguished between those churches which are accurately pinpointed (green) and those for which the general vicinity is marked (blue).