Before you start screening, you can export a list of references from title and abstract screening.

If you have completed title and abstract or full text screening and then try to export the references from that section, you will have an empty csv or reference manager file.  This is because the references are no longer located in that section.

When you have completed title and abstract screening, your references will be located in 'Irrelevant' and 'Full text review'. 

When you have completed full text screening, your references will be located in 'Irrelevant', 'Excluded' and 'Included'. 

You can export these references to a csv file or to your reference manager using the Export button on the Review Summary page and selecting the reference option and format from the drop-down boxes.