It'd be kind of wierd without scripts but 100% doable, when you start the game, make an event that asks if the player wants to play the game in EASY, NORMAL, or HARD, and if easy, make a switch come on called EASY DIFF, and the same for NORMAL and HARD, and then when you make events or enemies, make conditional branch or something, if EASY DIFF = ON, blaa blaa, if NORMAL DIFF = ON, blaa blaa, if HARD DIFF = ON, blaa blaa.
Not sure if I explained clear enough, but hopefully you'll understand.