How can I make it so stuff that spills over the edge of the page is "hidden". I would prefer something non-destructive I can turn on and off

Mock Up example : https://i.imgur.com/VWM3qXt.png

In this example, the black boxes go outside the page.... how can I make it so stuff outside the page is invisible?

(PS I couldn't workout how to post images)

For momentary clipping to the page boundaries, the f key is your friend.

For toggle on/off, the Document Properties dialog has a checkbox.

You could also use a clipping group, or a clipped group.

Thanks!