Hi. I'm looking for a way to make short blades do more critical damage. I have 0 experience apart from opening TCS and finding the global value of x4, so I would be grateful if you could point me in the right direction or tell me if it's hard to achieve.

Critical damage is dealt when the enemy doesn't detect the player and not in combat. That aspect can't be modifiied. So you can only deal only on critical hit per target. Your best bet is to stay invisible or sneak on your target.