* {
	box-sizing: border-box;
}

body {
	margin: 0;
	min-height: 100vh;
	display: flex;
}

.columns {
	width: 100%;
	display: flex;
	flex: 1;
}

.column {
	width: 100%;
	flex: 1;
	outline: 1px solid black;
	text-align: center;
}

.column [sync] {
	text-align: left;
	border-bottom-width: 2px;
	border-bottom-color: red;
	border-bottom-style: dotted;
	height: 0;
	text-indent: 0.5em;
}

.column [sync=""] {
	display:none;
}

* {
	box-sizing: border-box;
}

body {
	margin: 0;
	min-height: 100vh;
	display: flex;
}

.columns {
	width: 100%;
	display: flex;
	flex: 1;
}

.column {
	width: 100%;
	flex: 1;
	border-left: 1px solid black;
	text-align: center;
}

.column [sync] {
	text-align: left;
	border-bottom-width: 2px;
	border-bottom-color: red;
	border-bottom-style: dashed;
	text-indent: 0.5em;
}

.column [sync=""] {
	display:none;
}

Change border to dashed, move text for dividers above the line.
Change border to dashed, move text for dividers above the line.
