Let me just check I understand this ...

.. so if I just need to change MUX to control GPIO in I/O mode, I need that API to the SC to do this ..?
Where is this document .. ? (why there is no link to official latest version to it in the chip's UG?)
JUST making sure I need "that" highly protected Mux to do this -->

This UG part does not say which mux it is !

... "IOMUX chapter", where ,which .. ? There is sub-chapter / section on IOMUXD.
Would be awesome if NXP does in-the-doc links to what they refer to.