You can create and use a custom GameInstance BP the same way you would do in C++.
This GameInstance persists during level changes until you close the game again.
After selecting “GameInstance” for your new BP:
You can easily set this to be the standard GameInstance Class in the Project Settings:
And get the Instance Pointer in every BP (with casting so you can use your custom one):
If you have more questions regarding this topic, feel free to ask me (: