if you are using just windows you add the flag to a shortcut for the application. Rightclick the shortcut>properties>Target field = "C:\Program Files\iNav\iGuidance.exe" nowarning
using a button in RR the code for the button would be
RUN; "C:\Program Files\iNav\iGuidance.exe|nowarning"
using skinbedder, it uses autoIT to launch IG so you will have to edit the startup.au3 file found in the skinbedder dir (you will also need to install AutoIT3 to recompile the script to a .exe)
edit startup.au3 and edit the line
Run("C:\Program Files\iNav\iGuidance\iGuidance.exe nowarning", "C:\Program Files\iNav\iGuidance")
to look like above.