How to get a BP placed in level from game mode?

[Roy_Wierer.Seda145]

Programming Subsystems | Unreal Engine 4.27 Documentation

You can create a new blueprint asset and pick a subsystem as a parent class:

I am suprised not to see GameInstanceSubsystem in that list for me on UE5.1, see if it still fits your needs. Else creating one in c++ is easy as long as you know the basics of C.