I'm currently building my first custom map, it's a tower defense.
Making the terrain and the triggers wasn't too hard, but the Data Editor is giving me a headache.
I'm trying to make the Reactor a normally placeable building, so I can use it as a Mineral Generator.
The mineral-generating part works fine, but I spent maybe two hours now looking through all the data points in the Reactor unit and still couldn't find the right thing. I removed everything in 'Behavior: Built on', but that didn't help.
I then spent another hour trying to find help on the internet but I was out of Luck. Everybody just talks about Tech Labs.
Add-ons are a headache :). I think your best bet is to use or clone a regular building (NOT an add-on), making sure to clone its basic actor as well (but you shouldn't need to clone any models or anything). Then copy the "Events" field on the cloned actor, go to the Reactor's actor, and paste the fields there. Finally, either delete the cloned actor or get rid of all of its events.
I haven't tested this solution on your specific problem, but I have been able to swap actors this way with other things. Hope this helps!