This video introduces how to create a FlatBuffers Schema file to structure save data in Unity.
FlatBuffers Schema Documentation: https://google.github.io/flatbuffers/...
UnityFbs Github:
https://github.com/Wunder9l/UnityFbs
Direct flatc.exe link (Select your platform):
https://github.com/Wunder9l/UnityFbs/...
As the GitHub link states, there is a mild risk of downloading the flatc.exe file directly, you may download and compile your own from a separate website if that is a concern of yours. I have been using UnityFbs flatc.exe files without issues.