You can use the following js code:

Qualtrics.SurveyEngine.addOnReady(function () {
	const quest = this;
	const qc = quest.getQuestionContainer();
	const images = qc.querySelectorAll("img");
	const startingWidths = [];
	const imageMaxWidth = "${e://Field/imageMaxWidth}" || "unset";
	images.forEach((image, index) => {
		startingWidths.push(image.style.width);
		image.onclick = function () {
			const currentState = image.style.width;
			if (currentState == "unset" || currentState == "") {
				image.style.width = startingWidths[index];
			} else {
				image.style.width = imageMaxWidth;
			}
		};
	});
});

If you want to control the maximum size upon expansion, you can set an ED with the name imageMaxWidth to a certain pixel value (such as 200px).

Thanks for the answer @ahmedA !

Does it appear to be correct? Unfortunately, it doesn't seem to work with my current setup. The image I want to enlarge is located in section 5 of the Text/Graphic page.

Maybe your images are already at their full width.