You should add a "type" tag to your JSON. Type can be "enemy" or whatever other types you have.
Then just check the type on the way through the JSON and compare to the string "enemy" and only operate when that condition is true.
Thanks for the tip. I already figured out a workaround, in case anyone is curious:
Since my enemies exist on a tilemap, I loop through the tilemap and pop the JSON of each enemy on to the back of my array when exporting a level. On import, I loop through the tiles again, creating an enemy depending on what tile it hits and activate an event group that contains an "On enemy created" event, so each time an enemy is created at a tile, it loads the first object JSON in the array and removes it. Since I loop through the tiles in the same order on import and export, the order of the JSON objects is always consistent when importing back in.