I had once bought SimplePlanes from the App Store on my Mac and it was modded. My computer got wiped but luckily tonight I found a drive will all of my backed up SimplePlanes files on it. One of those files being all of my local data for SimplePlanes. the folder I found the stuff in was called com.jundroo.SimplePlanesOSX Unfortunately I am not sure if you will be able to find it on your OSX but surely did!
Nice. I place mods in a folder when modding with steam too.
See, that’s why you buy it on Steam for easy modding.