Translations:Help:Extension:Translate/Page translation administration/110/en

From mediawiki.org

Split: Clicking on this action icon parses the corresponding target unit and separates it into units such that the headers are separated from other wikitext. As a result of this, new units are added below the current unit. Use this feature when a section contains a mix of headers and other wikitext. In this case, you need to only copy the unit to align it with the corresponding header and then click on the 'Split' icon.