A recap of the font specification.

With text-box-trim we gain control over which boundary line text boxes are cropped to, and finally we can trim away this extra space to work with a font’s actual visual height.

One of the most common use cases for a lot of us is visually centering text within elements like buttons or notifications. This is especially handy for fonts that have awkward spacing like Josefin Sans.

There are plenty of creative uses [...] I placed headings with their baseline flush against sections below using negative margins. [Using text-box-trim remove the use of margins and put the heading just on the line of the next section, https://quarterre.com/studio]

Another example is to put the line on the font baseline like https://www.wepioneer.co/