bOverrideLightMapRes is a boolean C++ variable that is part of the UStaticMeshComponent. You don’t need to know C++ to change it, though; you can set it via a checkbox in the details panel called “Override Light Map Res”.
Because the entire engine is written in C++, all of the properties you change in the Details panel are really variables being set to the C++ objects underneath. Sometimes, in the documentation, they reference properties by their internal variable name.
Thanks for the patient answer. I need a 2nd coffee.
I blame my expereince in other apps where when you hover over a Editor paramater it automatically displays the actual property.