autopopulate column 2 in a SBS when a selection is made in column 1

So it appears working with SBS in the simple layout is quite complicated as the options are not longer arranged as tables.

Here’s a code that you could try.

Set the source and target as per your requirement.

Qualtrics.SurveyEngine.addOnReady(function () {
	const sourceCol = { question: 1, col: 1 };
	const targetCol = { question: 2, col: 3 };

	const quest = this;
	const qc = quest.getQuestionContainer();

	let rows = 0;
	const allInputs = Array.from(qc.querySelectorAll("input")).map((a) => {
		const obj = {};
		obj.question = parseInt(a.name.split("-")[1]);
		obj.row = parseInt(a.name.split("-")[2]);
		obj.input = a;

		if (rows < obj.row) {
			rows = obj.row;
		}

		return obj;
	});

	for (let i = 1; i <= rows; i++) {
		const rowInputs = allInputs.filter((item) => item.row == i);
		let currentCol = 1;
		let currentQuest = rowInputs[0].question;

		rowInputs.forEach((item) => {
			if (currentQuest != item.question) {
				currentCol = 1;
				currentQuest = item.question;
			}
			item.col = currentCol;
			currentCol++;
		});
	}

	const updateChoices = function () {
		setTimeout(() => {
			const sources = allInputs.filter((item) => item.col == sourceCol.col && item.question == sourceCol.question);
			const targets = allInputs.filter((item) => item.col == targetCol.col && item.question == targetCol.question);

			sources.forEach((src, index) => {
				if (src.input.checked) {
					targets[index].input.click();
				}
			});
		}, 100);
	};

	quest.questionclick = updateChoices;
});