This tool would be so fun and I would definitely use it.
But ALSO! The best thing about writing injuries is that there is so much variation.
I spent a few years as an EMT, and I saw people walk away from vehicle rollovers with nary a scratch... and also, I saw people break their knees because they sat down. I've seen a guy get lifelong impairments out of falling off something twelve feet high, but I know someone who survived being stabbed over a dozen times with no lasting (physical) injuries. There's range.
In nearly any given situation*, a realistic level of injury is anywhere from "Dies within five minutes" to "Dies 73 years later surrounded by grandchildren and great-grandchildren, having zero long-lasting repercussions from that incident."
*Not every situation, mind you; papercuts are generally exempt
If you don't mind a ramble (because I haven't done a fun character injury ramble in a while so I shall use this as an excuse)...
The key to writing realistic injuries is to start with what you want to happen. It's your character and your scenario, so start with what you want to happen for Plot Reasons.
You know your character gets in a car crash with a wall, and you want them laid up for a week, but able to move around with minimal pain soon after. Cool. Now that you have your desired outcome, you can run through the scenario. You won't want your character ejected or to have a major head impact with the windshield, so they were wearing their seatbelt. You want them to still be able to walk, so the dashboard probably didn't crumple in on them. That means they were either in a car with good safety ratings, or they weren't going super fast, or a combination thereof. But you do want them a little bit injured, enough so they don't want to go on that hiking trip for another week, so make sure they were going fast enough to get some good ol' whiplash.
You want your character to make a dramatic exit out the window, and you want them to be limping a little for dramatic effect as they head off into the forest surrounding the castle. Nice, we love a good dramatic window exit. But you want to make sure the character won't be out of commission for the battle in a fortnight's time. This could totally be a first-floor window, or even a second-floor one. But what if it really needs to be the fourth floor, for pre-existing scenario reasons? Well, maybe there's a balcony halfway down. Or maybe there's a nice slanted roof underneath that broke their fall. Or maybe the castle is built into a cliff so the windows on that side of the castle are only ten feet up. Or maybe they clung onto ivy outside, which ripped out of the wall a bit but was enough to slow them down. There's all sorts of ways you can play this off!
Rather than trying to make a scenario and then fitting the injury into it, come up with the injury (or at least, level of injury) and plan out the details of your scenario around it.
The only caution is to make sure to build scenarios realistically—like, I could totally see a character being able to keep going after being stabbed because it was a shallow wound. But if they get a shallow stab wound... and they only get ✨grazed✨ by a bullet... and they happen to survive a terrible car accident because they were in the best possible seat... AND they were pushed out of an airplane but their BFF managed to skydive right out after them and caught them... that's getting to be a little much. XD Any of those is realistic except maybe the last; IDK, I know injuries, not skydiving, but too many near-misses in a single story starts to feel like plot armor.
But yeah. The range of possible injuries from any given scenario is immense. But if you figure out how much you want to injure the character (or how quickly you want to kill them, you evil author you), you can then build out the scenario so it makes sense, and research gets a little easier too because it narrows down what you're looking for.
