Working version for testing here
Nvidia added support for prime-offloading in the driver 435, which is much more stable than unofficial utilities like bumblebee, while still allowing usage of both the Intel and NVIDIA card without restarting XOrg (prime). Additionally, prime-offloading doesn't face the issue @jonathon outlined in this post. The reason I'm bringing this up is that bumblebee just isn't stable enough. I've helped multiple users that faced issues with bumblebee (either not allowing their laptop to boot at all or crashing steam games) which were solved by setting up prime offloading instead.
Currently, the manual setup is as follows:
removed so nobody does this manually. check edit history if you still need it
(Setup stolen from NVIDIA 435 driver looks exciting)
Additionally, the manjaro team could add code to run steam using the nvidia card to steam-manjaro.
If nobody from the manjaro team wants to pick this up, I'd be glad to test and create a config for mhwd.