Exactly, the Fn-key itself is not sending a modifier key-event to the upper layers, so if ex. Fn+Left/Right is not triggering the BIOS to generate some dedicate

Exactly, the Fn-key itself is not sending a modifier key-event to the upper layers, so if ex. Fn+Left/Right is not triggering the BIOS to generate some dedicated key-event (ex. translating it into a Home/End key), a keyboard mapping tool in the OS receives only the Left/Right key-event...