M408 S0 and S1 return a flat JSON object. M408 S2 to S5 return a nested JSON object. The parser in PanelDue didn't originally work with nested JSON objects, but I extended it a few versions ago. There were bugs in the original implementation, but I fixed those when I used the same parser in another project, and I back-ported the fixes to PanelDue in the latest revision. So it should be possible to use S2 instead of S0 now, and also to use S4; but you will need to change the variable names in table ReceiveDataTableEntry in PanelDue.cpp to match the names used in the S2 response.
There is already code to process a M36 response, but currently it is only used in to display file info after selecting a print file.
