Ok, I managed to cut the script you gave me to strictly necessary for display hidden skills, after the game gave me thousand errors when I just pasted the whole in then removed the check for activating the script.

Now looks safe, thanks.

Secondary skills scrolling can not 100% replace Display Hidden Skills, since it does not allow leaning new skills at huts, universities and scholars once you had the 8th skill, while Display hidden skills allow it by using the commander's hat (which gives always First Aid) equip/ctrl + click on experience icon then swap skills between hidden and not hidden. So a new skill emplacement is free.

So it had its purpose, especially in chinese maps by Woodmelon where this functionality is part of the game.