The most popular tool for this is the Ren'Py Save Editor by the_bobig (formerly known as the Renpy Save Game Editor). Official GitHub Link
https://github.com/RenpySaveEditor/Renpy-Save-Editor
Paradoxie Save Editor: The saveeditor repository on GitHub is a privacy-focused, universal online save file editor that supports Ren'Py along with other engines like Unity and RPG Maker.
For Python scripts, you may need to install dependencies via pip install -r requirements.txt and run the tool using python main.py.
# Inside a Ren'Py script or using renpy.loadsave module
import pickle
with open("your_save.save", "rb") as f:
data = pickle.load(f)
data["stats"]["health"] = 100
with open("your_save.save", "wb") as f:
pickle.dump(data, f)
%APPDATA%\RenPy\YourGameName\~/Library/RenPy/YourGameName/~/.renpy/YourGameName/