Settings apps such as macOS, Windows and KDE Settings can look to busy and make newbie users confused. A toggle could reside in the sidebar to switch between the simple/newbie and advanced mode.
This isn't something we think would be a good idea. See https://community.kde.org/Get_Involved/Design/Lessons_Learned#Basic.2Fadvanced_modes for an explanation as to why.
Hmmm, makes sense. Thanks!