tbh, if I made a horror game I wouldn't use jumpscares at all, since, in my opinion, it's just a cheap tactic to startle people and doesn't have too much to do with horror itself. Horror is rather about the atmosphere, the creepy feeling of paranoia or of being in a dangerous situation. Which can be built best with sounds, music, fitting graphics etc. I don't think that much of jumpscares...
Good jumpscares though, hmmm. Good example that is effective is like in the witch's house when you come close to something and suddenly a bottle falls off the cabinet and crashes on the floor (with loud sound effect, totally overused but if executed well it can be quite effective). The randomly moving objects and big amount of jumpscares in hello hell-oh ? was pretty well done too, and if you look for a way to make your player shit their pants you should play it moves and see how it uses the mixture of atmoshpere, music, graphics and gameplay to scare the player (pretty good horror game in my opinion xD). My advice is just checking those games out and figuring out? idk, I haven't played or watched good horror rpg maker games in a few years sooo. Also a game which does very good with scaring the player was TAUT. It worked a lot with graphics
seriously i dont know much about jumpscares. uhmmm.. this is hard to come up with ideas for some. One I found pretty interesting is if the picture/map changes into something gorey (the room but just with a lot of blood, weird faces on the characters, text on the walls or floors) for a few frames, like less than a second to get the player like "what WHAT HAPPENED"