Currently XenForo provides no integrated functionality to merge changes made in a child style into a parent style. This is a small, standalone tool I wrote that uses exported XML files to merge a child style into a parent style. If you wanted to merge two currently installed styles, the process with this tool would be like this: Export both styles. Upload xenforo_style_merger.php to your server and then access it in a browser. Upload both exported XML files using the form, and then download the outputted file. Import the outputted XML file to your XF installation. Again, this is completely standalone. It does not integrate with XenForo in any way. The interface is very basic, but that's not what I was focusing on. It currently supports merging Style Properties, Style Property Groups, and Templates. I'm not sure if there is any other style data that needs to be merged, because I only tested this on a couple of styles. This is provided as-is, with no guarantee of support, although I'll do my best to answer questions and fix bugs. If you find any bugs or have any questions, please post in this thread. Thanks.