If it is a NMEA 2000 depth
sensor, then OpenCPN cannot connect to it unless you install a NMEA 2000
to NMEA 0183
converter, such as an Actisense NGW-1
However even if a converter is installed, OpenCPN is not capable of configuring the sensor for a number of reasons. Firstly OpenCPN does not have an easy option for sending "one-off" custom NMEA 0183
sentences to a device, but more importantly, to the best of my knowledge there is no NMEA
0183 sentence that corresponds to any of the NMEA
2000 messages that are used by manufacturers to configure their NMEA 2000 devices.
Also the answer depends on which model Garmin depth
sensor you have. For example I do know that a Garmin GDT 43 does use standard (ie. non proprietary) NMEA 2000 messages to configure settings such as depth offset.
For some gory details on configuring a related product, the Garmin GST 43 refer to https://mt.panbo.com/2016/12/garmin-...-triton-2.html