If you pickup an elytra then it will automatically drop it or remove it from theg inventory depending on the settings of the gamerule that is added by the mod.
/gamerule elytraDrop true (Default) - It will automatically drop the elytra to the ground if you have an elytra in your inventory.
/gamerule elytraDrop false - It will delete the elytra from your inventory if you have an elytra in your inventory.
