I'm very happy there is now (hopefully) a straight forward was to use MODBUS with eISY, the plugin I found on Polyglot is
ModbusTCP
Modbus TCP allows you to define your Modbus registers in a JSON file, upload it and leave the rest to IoX. No coding is necessary. Make sure the file is named modbus.iox_plugin.json
Now I cannot find ant help or examples or documentation on how to configure this JSON file, or how to actually access the registers in the admin console or tie them to command/statuses.
This plugin is built by UD, so I expect some guidance. I understand it's free, but at least and example please. Thank you so much.