User:Ahecht/Scripts/infoboxgap.js is a user script that assists in renumbering infobox labels/data/classes, so that a new line can be inserted in the middle of the infobox. Based on User:Frietjes/infoboxgap.js, this version is modified to allow the size of the gap to be specified.
To install, add the following to Special:MyPage/common.js:importScript('User:Ahecht/Scripts/infoboxgap.js'); // Backlink: [[User:Ahecht/Scripts/infoboxgap.js]]
When editing an infobox, "infobox gap" and "infobox renumber" will appear in the left sidebar tools section. Click infobox gap to insert a numbering gap at a specified place (typically so you can add a new parameter or series of parameters there), and "infobox renumber" to renumber the infobox to remove all numbering gaps.