Would it be possible,when opening the galaxy map,and “hovering” with mouse pointer over each system ,to show which system contains,Rylan,Merlin,and Titan,certification stores, so taking the some of the guesswork out of where to go,when trying to track down a particular skill,or a list of these systems either in drop down menu,or in the forum.
The first port of call for locating anything like this would be one of the main hubs:
It is unlikely that you will find a skill store on a far flung planet in the middle of nowhere…
Some players may have lists, but you should find this a solid start 
I have noted the following so far. I know more stores have been added so I doubt this is complete. Nor have I been to every system.
Merlin - Terra, Midguard, Amunra
Rhylan - Arcadius, Arlington, Coleport, Dunal, Epsilon, Inception, Jerico, Midguard, Monsoon, Provenance, Terra, Titans Rest, Xantana
Titan - Hellicon, Provenance, Servitude, Titans Rest, Xantana, Zeonis(x2)