To clarify my original comment, when using an Apple Magic Mouse, the scroll to zoom feature is overly sensitive and will fly in/out at the slightest touch. It's an essentially unusable feature with this mouse; hence the request for a key command.

Those are helpful, but really what I'm looking for is more like guides in photoshop:

https://helpx.adobe.com/photoshop/using/grid-guides.html

I had posted a similar feature request over a year ago, but it does't seem like the updated grid functionality has been implemented. http://support.vertabelo.com/topics/230-adding-rulersguide-lines-to-help-with-positioning-elements/