Kevin,
First of all, I’ve got it! For some reason I was thinking that Timeout is in seconds, but seems to be in milliseconds. So, I was able to read my first register 
Regarding the settings, there is function code and offset for the address. According to my experience (that might be very limited comparing to other control engineers/forum members), the combination of those settings differs from one to another modbus implementation. I would say it would be nice to have “default” Losant settings and also a leverage to change it.
There are some modbus tools that allow to give a wide range of settings and preview bytes you send to the device.
The most convenient tool for Modbus RTU testing I’ve used called Simply Modbus. I will provide a screen shot for your reference, otherwise there is a demo version available on the manufacturer’s website
