If first attempt to refactor was over-engineered. They same will happen with the the new stack. New tools won't resolve problems. Start deleting the code.
"We know, for example, that iterating on existing solutions is more likely to improve software than a full rewrite. The dangers of full rewrites have been documented. Joel Spolsky and Stack Overflow described them as “the single worst strategic mistake that any software company can make.” - Kill It with Fire - Manage Aging Computer Systems (and Future Proof Modern Ones) by Marianne Bellotti
in emacs org-mode you can archive some tasks, text - it will move it to another text file ex. archive.txt with the timestamp or archiving it. Beside this keep your file in git. so you delete text & make explicit commit message that something was removed.