The Omni has four analogue signal clip indicators:
Two are associated with the preamps, to help you set a suitable position for each of the rotary gain controls.
The other two monitor the output level of the Omni mixer, with 'clip' indicating a level of 2dB below clipping. As you say, these clip LEDs are prior to the send/return sockets, so I suspect it will monitor the level going to your compressor input.
As long as you set any input gain control on the compressor to a suitable value, you can still rely on the Omni clip indicators to show the the compressor is close to being clipped.