Q: What could I do if I want to extract some irregular fields that are not provided by all items?
Two methods are provided in this case.
One is to use the Backup position option, if the element you want has only two locations on the website.
Choose the irregular field under "Extract Data" action. ➜ Choose "Customize Field" and "Define ways to locate an item".
Tick the option "Try Backup Position".
Click the field's another location and choose the "Set as backup position of current item" option in the pop-up window.
Then the XPath of the element will be generated automatically in the Backup Position textbox. Click "OK" and "Save".
The other is to manually modify the XPath of the irregular fields. Also choose the irregular field under "Extract Data" action and “Customize Field” as well as “Define ways to locate an item”. Then you could enter the XPath in the “Matching XPath” textbox.
To find out more details about how to manually modify the XPath you could click HERE.