This could just be an issue to do with it being on 1.15.2 with LWJGL 3 and the GLFW implementation, but the windos game bar doesnt render on top of the minecraft window.

I think I found a fix for this a while back, but it's not in the final code as there were bugs with it. GLFW on Windows is a bit buggy, and it's not helped by terrible Intel/Nvidia hybrid drivers I use. I'll see what I can do though.