From memory as not at car at the moment... on the physical buttons below central display press the one labeled home, swipe the whole display to the right, at the bottom of the display iirc there's an icon that looks like a plug, tap it (or I think you can do the same thing by tapping the right hand side of the screen which is EV settings related), then there should be a menu on the left that you can scroll down, there's a charge limit option there that on tapping brings up both DC and AC sliders where you can set the limit.
Or via the (new) Kia app tap the control option at the bottom, then top right tap where it says EV, this should bring up battery section, just below where you tapped EV there's a sort of gear icon, tap it and you'll see a target charge level option, tap it and you're at the sliders to set level, don't forget to tap save at bottom after changing.
Intuitive it is not!