If there is an option to duplicate the Text Styles / Color Styles folder then it makes it easy when creating design systems. Attached is a screenshot of the idea.
Beware of that workaround if you already have published styles. It has broken a lot of my applied styles in other files (swapping them for the duplicate)
There is a workaround that actually works:
1- Cut the styles you want duplicate
2- Undo so you have your styles back (now the styles and folder structure are copied to your clipboard)
3- Paste the copied styles into a new Figma file then save the file
4- Close both files
5- Open both files again
6- Now you can edit the styles in the new file then cut and paste them into the original file
7- DONE!