Technologies.xml is the base game tech (most techs)I too I am trying to get the tech multiplier working. I have no problem taking the time to adjust each civics and technology manually, does someone have a complete list?
I found many listed under Technologies.xml, but not all. Same issue with civics.
Technologies_xp1.xml are the Rise & Fall techs
Technologies_xp2.xml are the Gathering Storm techs
The same is true for civics, units, buildings and most other things. This is part of why it is easier to simply apply a multiplier via SQL to hit all of the techs (except most people miss the random tech costs). If you really want to adjust them all manually you'll find everything but the base Technologies.xml in the DLC/XP1 (for R&F) or DLC/XP2 (for GS) folder. Keep in mind that the tech cost is what determines which column it will be placed in on the tech tree so if you make a tech cost less than one of it's prereqs in the same era it will look messed up and the techs that use a random prereq will not use a prereq that is more expensive (which explains the issue @Ellye is having).