Hi,
Currently, there are no config option to show extra fields into the properties list page. There is only one way to show extra fields into the list page is modify the source code page.
You can hack into this file
components > com_osproperty > templates > default > listing.html.tpl.php
to show one field, we use php function
HelperOspropertyFields::showField($field,$pid);
$field : Object of extra field that you want to show
$pid : Id number of property
Thanks
Dam