- Select the node or label in question.
- Go to the properties view in the lower right corner.
- Set option "Size" in the "Label" section to "Fit Node Width" or "Fit Node Size".
- Set option "Configuration" in the "Label" section to "Cropping".
Automatic text wrapping uses the rectangular bounds of a node to determine when to break a line (i.e. if you use a non-rectangular shape like a circle, the text will not fit into the visual shape).
Moreover, the "Cropping" configuration only supports plain text, but no HTML formatted text.