The SR48 Ground Bus Assembly, part # 7051A2020 can accommodate up to 72 landed wires. However, if you need to land more than 72, you can Scotch-Lok (14awg) or Wago (12 awg) or other sutible methods into the existing landed ground wires, or install a utility box next to the rack. Within this, all of your grounds can tie to a central ground(s) that run to the gang plate in the rack.
The smaller Sensor dimmer racks have even fewer ground terminals. Use the same methods described above if you have too many load ground lines.