How to add breakpoints for text styles
Text style breakpoints allow styles to have a different size or line height across breakpoints.
Every text style you create comes with different breakpoint sizes. It's important to realize that the text style breakpoints are not linked to your canvas breakpoints, because multiple pages can have different breakpoint sizes, but styles need to work across projects.
If you create a new text style it comes with three breakpoints defined by default. The breakpoint sizes are based on the ones you defined on the current page, or they use the defaults. Breakpoints are defined as L M S (as in Large, Medium, Small).
The different breakpoints get smaller sizes based on the popular major thirds algorithm. You can go in and tweak them however you like, as well as the line, paragraph and letter spacing.