Hi dc42,
First of everything thank you a lot for the answer!!
I was near to put the board in a corner and roll back to smoothieboard…

My thought about how to organize the documentation is very simple:

First of all, the technical documentation about the board, including pin assignment and control, expansion board and daughter boards (PT100 etc) has to be documented with pictures and pin number assignment and how to control each of them (if not already done)

I would start to organize and divide the docs into sections for each frame( Delta, CoreXY, Cartesian, etc)
Many commands in the documentation are referring to a delta setup, but then indicated and assumed as good as for other frames, which is correct as they basically are always the same, but as the RepRap firmware has a lot of commands and variables(options), that could be confusing for a novice (like me for example).

Second, (I know can be boring) I would create various sub-sections for each frame (XY Axis setup and enstops management(fully documented including stall detection management), then Zaxis setup and Z height calibration with clear examples, bed leveling, and bed compensation(mesh) and examples to "how to" with sections of Config.g and Bed.g files clearly explained and so on, then last but not less important, temperature tuning and the cooling fans with the long list of examples all collected together and VERY well explained.

It would be very important to just click on the page of the frame (and sub-menu) of the part you need the setup or help for.
Counting on pictures and detailed drawings would be helpful always...

At today, for example, I am still calibrating the nozzle, as the temperature is not stable, and with the same hardware setup as it was on the smoothieboard, i have to increase the temperature about 30 degrees to print the same material...

I am sure Duet is a great board, but if not clearly and fully explained it cannot be enjoyed properly at 100% and would be a shame.

I don't know if what I said make any sense, and maybe is not clear as my English is very bad (I apologize for that), and anything I said shouldn't be interpreted as a criticism, but just as a constructive suggestion.
I am obviously more than happy to help if I can.

Best regards
Emanuel