Please refer my previous article to learn more about creating NINTEX forms in SharePoint 2013 Online.
I have created a custom NINTEX form in the custom list named Custom List A. In this blog you will see how to export and import the NINTEX forms in SharePoint 2013 Online.
Export NINTEX form:
Navigate to the Custom List A. Click on List tab and then click on NINTEX Forms button in the ribbon interface. Click on Export button in the ribbon interface. Save the xml file on your desktop.
Import NINTEX form:
Navigate to the Custom List B. Click on List tab and then click on NINTEX Forms button in the ribbon interface. Click on Import button in the ribbon interface. Select the exported xml file and click on Import button. Click on Publish and Close button in the ribbon interface. NINTEX form is imported successfully in Custom List B.
Thus in this blog you have seen how to export and import the NINTEX forms in SharePoint 2013 Online.