I'm not familiar with Eclipse, which perhaps explains why I don't fully understand what you mean.
Is the possible to import/link more than one element from a schema file?
Any global element declaration (that is, an xs:element with a name attribute appearing as a child of xs:schema) can be used as the root element of your instance document, if this is what you mean.
Also is it possible to import complex data types instead of elements in the XML document?
Any global type definition (that is, an xs:simpleType or xs:complexType with a name attribute appearing as a child of xs:schema) can be used as the value of the xsi:type
attribute in your instance document, if this is what you mean.