Adding to this, it doesn’t hurt knowing multiple readings… I usually just type the first reading that comes to mind and if wanikani complains, I’ll type another reading.
If that’s insufficient for you, userscripts to the rescue!!! This userscript tells you which reading (on or kum yomi) wanikani wants to know
For more userscript goodness, checkout the The New And Improved List Of API and Third Party Apps thats a mouthful