This is a third-party script/app and is not created by the WaniKani team. By using this, you understand that it can stop working at any time or be discontinued indefinitely.
I don’t know of such a script, so I created one for you:
WaniKani Later Crabigator
It adds a button “Later” to the right of the input box, which allows you to push the current review item to the end of the queue. It will reappear within the last 10 reviews. It probably won’t work if you use other reordering scripts – I haven’t tested this. The script is based on @seanblue’s WaniKani Prioritize Overdue Reviews.