My 2018 Outlander Sport has an height adjuster for the headlights there and a couple of blanks next to it.

 

Here is some pics of other options for some of those buttons....

https://mitsubishiforum.com/forum/mitsubishi-outlander-10/what-button-51056/

 

Discovered on my 2016 Outlander, that car has wire harnesses behind the cover of the unused 5 switch locations.
Just wondering if somebody could tell me, what each of these 5 switches designed to do and maybe speculate about the possibility of installing some-kind-of pushbutton switch to activate any of these options ?
Thanks!

This sounds like a fun project to do. Please keep us updated on your progress.
Here is my contribution - I found this picture on the internet for 2018 Gx5h (highest trim) with all the five buttons populated. This is for a UK spec, but I guess the buttons would be the same in both left and right hand drives.

 

I have the first button on my car that opens the boot. rest are all blanks. Looking at the picture above, they all seem to be dependent on some sort of distance sensor which is not on my car.