Success!
After going into Expert mode in the Bimmercode App, you have to change the following:
Headunit(HU_NBT) > Expert Mode > 3000 HMI >
ENT_MIRACAST to aktiv
ENT_MC_WLAN_STREAM_DMP to aktiv
ENT_MIRACAST_DISPLAY_SETTINGS to aktiv
ENT_MC_WLAN_STREAM_DMP_COVERART to aktiv
ENT_MC_WLAN_STREAM_DMP_VIDEO to aktiv
Headunit(HU_NBT) > Expert Mode > 3003 TELEFON_TELEMATIK_ONLINE >
WLAN_WIFI_DIRECT to aktiv
WLAN_STATUS to aktiv
Select code. After the car reboots, you should see the screen mirroring option when trying to add a new device.
I'm pretty happy with this option. It would be perfect if there was a way to zoom in to full display during screen mirroring. I can zoom in to full display with a video on USB.