Thanks for sharing, tried it out a little while ago and can confirm it worked. Lots of info in the engineering mode but didn't come across any hidden features or anything except for what looked to be a screen capture mode, presumably for sharing bug reports.
Its precisely not intended for consumer usage, its only for kia service technicians, but personally, as someone who works in tech, I just like to be able to poke around and know what hidden information or settings are available.
It can be interesting as a tech to check for some options to enable/disable or change some limits..
But it requires caution, In renault some people wrecked their car and has to re-install software to get their navigation working again.
Since the car more and more relies on software it means the impact of wrecking such a system becomes bigger. Altough interesting it is also tricky..
There are ways through the engineering mode that various android settings can be changed and such to allow you to install third party apk's for youtube and other applications. All of this is well documented on various online forums.