You can select the enemy group that defends each object, but then the mission engine will choose which members of that group to spawn, as well as their numbers. If you try building a custom group that just has your boss in it, there is a good chance that you'll get multiple copies of that boss (learned that one the hard way).
Currently, you cannot specify a single enemy to defend, nor a single named enemy and a group. However, we can always hope for that capability in future updates.
I am currently working on a mission where you have to destroy 6 anchors and then an elite boss is spawned. I would also like to have specific bosses spawn next to these anchors to defend them, but I can't figure out how to do this.
Is this even possible with the current system? If so, could someone please walk me through the process for accomplishing something like this?