How do I hide an object in the layout editor?

For example, in order to select an object underneath. I would imagine this function exists in the editor, but I can't find it anywhere.

if the images are on different layers, you can lock the layer of the object above with the padlock in the layers menu, doing so the things on that layer can no longer be clicked and you can easily select the ones below

if the images are on different layers, you can lock the layer of the object above with the padlock in the layers menu, doing so the things on that layer can no longer be clicked and you can easily select the ones below

Is there a solution if they are not on different layers?

I'd like to know too, but sadly I don't think so

If you want to select an object that's underneath something else, you can hold the tab key and click the object - the selects the next object in the Z order. It's mentioned in the Keyboard Shortcuts section of the manual.

And while you're working on something, you could always drop the opacity on objects you need to see beneath too.