GLC Transfer Case Limp Mode

Slipping and rough shifts combined with a potential transfer case limp mode is not ideal. The ABS system influencing the transfer case control module is plausible, as they are interconnected. It's possible the system is limiting torque to protect itself. Have you scanned the vehicle for any error codes? That would be the first step.

I haven't scanned for error codes yet, but I will soon. Would a generic OBD2 scanner be sufficient, or is a more specialized Mercedes-Benz diagnostic tool required to properly read the codes related to the transfer case and ABS module?

While a generic OBD2 scanner might pull some basic codes, you're better off using a scanner capable of reading Mercedes-specific codes. A generic one might not access the transfer case control module or give you the detail needed from the ABS system. If you can't get your hands on a more capable scanner, it might be worth taking it to a qualified workshop for a diagnostic check.

I took it to a workshop to get it scanned. The limp home mode was triggered, but there were no actual faults. The control module was reset and the system recalibrated and that resolved the issue. No repairs were needed, so the cost was 0€.