Clicking & Holding/Dragging Doesn't Work in the Creator, and Probably Camera too

So far, it's only happening in Fullscreen mode, but it's still very slow and delayed when I try to drag/resize features. Everything else runs at a pretty normal speed, so as far as I can tell, that means my Mac can handle it, but for whatever reason, it doesn't like me trying to click and drag (rotating the Sim, adjusting features, etc.), and I'm worried that will carry over to the in-game camera. :/