If youâre on PC I highly recommend the double check script, I wouldnât be using Wanikani without it: [Userscript]: Double-Check (Version 2.x)
Wanikani says the reason they donât have a built in undo button is because they want to prevent users abusing it, but my tinfoil hat conspiracy is that itâs just so that you stay on the same level longer when you make typos so your subscription runs longer