Change font family all text style in a library file

Get yourself Styler plugin. Then create an empty page and run Styler > Extract Styles. It will output all your text styles into separate text layers. After that you would need to run Styler > Detach styles to get them raw. At this stage you can adjust all of them in bulk like regular text. When you are happy with the result, select all and run Styler > Generate Styles.

It would match a layer name with a corresponding style name and update them with text properties on that layer. Real lifesaver it is )