I have written a bit of code lately which automates the process of constructing chemical reaction energy level diagrams rather well. It’s called rxnlvl. It’s written in Python, outputs to SVG (Scalable Vector Graphics) and is GPL3. I’m not a ninja programmer by any stretch of the imagination, however the program is basically functional, and in my estimation yields quite attractive results.
You can check it out at https://github.com/eutactic/rxnlvl
Enjoy, and if you find it useful I encourage you to show me what you’ve done with it.