InfoboxEditorPreview(or InfoboxPreview) adds an option for previewing the infobox markup in edit mode.
If the currently edited template is an infobox, the mobile preview button will be replaced with an infobox preview one. When clicked on, a dialog appears which shows invocation examples for your infobox. The examples are taken from articles which embed the currently edited infobox or (if it is a draft) its parent infobox.
In the editor next to the preview you can play around with the example invocations or write a new one from scratch.