My model’s X axis aligns correctly with the world’s X axis, true, but the issue is that my model’s X axis is not what I would consider “forward”, since it is pointing down my model’s left arm. The way I imagine it, my model’s forward axis should be pointing out of my model’s back, since I am looking at my model from the front in my modelling software, down the forward axis. The only way I would consider the forward axis being down the left arm is if UE4 coordinate system is thought of as a side-scroller, then it makes perfect sense.
I guess my issue is more about why the thumbnail disagrees with the scene. The thumbnail appears to be looking down -Y for the capture, which doesn’t make sense to me. I could adjust the thumbnails like you suggest, but I pulled up some UE4 sample content projects, and all of their static and skeletal meshes are all suffering from the same issue: the thumbnail is correct, but the model’s forward axis is down the model’s left arm.