Steps to replicate:
Create any new car
Replicate trims until you have more than 10
Scroll bar will highlight, but is inoperable - rendering your ability to modify the 11th trim impossible.
Mouse wheel scroll has no effect (or it’s laptop equivalent touchpad scroll).
Note: I did notice the game rightly gave a warning about “too many items being produced in a factory, severely reducing its efficiency”. However, I hadn’t gotten to the factory setup yet where I planned to create multiple factories with only a few trims per factory. So that warning, while warranted, seems a bit premature.