Is there a less tiring way to type in japanese? I think I'm stressing my arms and wrists too much

This isn’t really about the particular issue you’re talking about, but just in case you’d be interested, I thought I’d mention it.

If you’ve found that needing to press the enter key twice after every WaniKani review item to also be tiring, there’s this script that eliminates the need to do that. The way it works is, if what you’ve typed up is correct, then your answer is automatically entered, and it moves on to the next review item. One drawback is that it does make it possible to cheat, since if what you’ve written doesn’t automatically enter, you can figure out that isn’t what was wanted and change your answer. At the same time, though, sometimes the reason it doesn’t enter is just because of a typo or a negligible rephrasing of the answer that will get accepted anyways. So that ambiguity makes it easier to just go and press the enter key on the occasions that it isn’t automatically entered.

There’s also this script with a similar concept, but with more options when it comes to managing typos. I personally use the former, as well as a now unmaintained script with extra features, but to be honest, this second one looks like it might be better. (I only came across it just now, while finding out the other script I use isn’t maintained anymore.)

One reason I ended up taking a one year long hiatus from WaniKani was because of the strain it caused for my little finger from needing to hit the enter key so many times. (Just to clarify, though, it wasn’t a year because my finger was hurt that long. I just decided I didn’t want to do it anymore if it was going to be like that, and it took a year for me to come back and find out about scripts that could fix the problem.) So I hope this can be of some help to you as well.