I have also been on the path to having variables in file names that I render. Specifically I am currently trying to have camera names in there. I tried the Oscurart Tools and they are a little limited, not to mention have little to no documentation at the moment.
I however found an addon that does do Global variables in the output path much better: it is called loom https://github.com/p2or/blender-loom
It isn’t perfect as of yet, but it certainly has a decent variety of variables. They don’t work in situations outside of just rendering the current scene, but I have made a request to expand this in 2 ways that may or may not come through.
I believe many people can find this useful. Hopefully even more so if the addon gets attention and love.