Solved it!
Modbus on Solaredge seems to be very picky in establishing connections. Had to stop home assistant (complete shutdown), disconnect the SE inverter on AC and DC, shut down entire Victron system. Start up sequence: Home assistant incl. modbus proxy, SE inverter, and Victron system.
After HA established a connection to SE i powered up Victron and was able to manually add the proxy IP as PV inverter. Most important was to switch to modbus ID of SE inverter to 126 on all devices and platforms.
One open issue remains: While I can see the AC output of the SE inverter as PV generation on Cerbo, Victron can’t distinguish between solar power and DC coupled battery power from SE inverter. I understand, that this is due to AC coupling but was wondering if there is a way to get that information to Cerbo via Home Assistant. HA has all the required information as it still receives the detailed SE power breakdown via the modbus proxy.
Any input is highly appreciated!
Cheers!