You can add line breaks to shape and connector labels.

Press Shift+Enter as you type the label text to add a line break.

Open this example in diagrams.net

Line breaks are only possible when you use HTML labels, and with word wrapping enabled on shapes. Both are enabled by default.

Re-enable HTML labels and word wrap

If you find a shape or a connector doesn’t allow you to add a line break, edit the shape style to re-enable these two options.

1. Select the shape, then click Edit Style in the Style tab of the format panel.
2. Add the style options: whiteSpace=wrap and html=1, as shown in the image below.