-Triggers??? Why bother including it with the new galaxy forge if you can't do anything at all with it?
It was planed but never finished. I wouldn't get your hopes up on it.
-Neutral colony placement (Why is there still no way for planet start with a neutral colony? I’d love to make a map where TEC Rebels’ research option Truce Amongst Rouges plays a larger role)
You can in the map designer. However it actually doesn't help with truce amongst rogues, its actually bad since you'll become allies and you can NEVER colonize that planet after you research it.
-Consistent Artifact placement (most of the time when I place artifacts the planets end up with the right one, but I still see artifacts being swapped for another a lot)
This happens when a planet you place an artifact on also gets a random artifact, since planets can only get one artifact at a time. If you have a map where you need a placed artifact to work, try lowering the artifact density (even to zero), you can always manually place more artifacts to make up for it.