Bug 14576 adds a new syspref that accepts YAML for determining how the rules are applied. While there are other prefs accepting values in the same way, we should not expect users to understand YAML text formatting and should offer an easier option for entering the data We should decide on a best practice here for adding these guis. One option is to add pages on admin, however, I think this could get overwhelming the more sysprefs that use this method. I would propose adding a popup editor that will allow for easy entry, this editor will populate the syspref value so that advanced users can still access directly. Welcome to hear other thoughts, will proceed as proposed until then.