Theres a few different ways to spawn enemies. You could instantiate a enemy on a key press or enter a trigger collider to spawn the enemy so I would say yes.

This can be done with Events (map/script events or via the "exec" dev console command):

spawn=<enemy category>,<X>,<Y>

So spawn=goblin,10,20 will spawn any enemy with the category "goblin" at position (10,20). If you want to spawn a specific enemy, it will need to have a unique category as part of its "categories" variable.