Many thanks for your answers, and reaction.
In fact as you know, there is several technical ways, one is described by David for exemple (HFI), but they also exist the PLL or/and backemf sliding mode observer or others observers to get back emf and so on.
There is ODRIVE, VESC for exemple that uses a mode here above.
My question just was to know if it was possible to implement this in SimpleFoc easly, because it is interesting to get this for some application ?