Use the Minimum Scale Factor modifier to allow a Text layer to fit its parent by shrinking rather than by truncating when the space available decreases. You can set the Minimum Scale Factor to any value greater than 0 and less than or equal to 1. The default value is 1.

For example, a Text layer with a Minimum Scale Factor of 0.5 will shrink its font size to as small as half the actual font to fit into a smaller space.