In the source datasource, select one or more interfaces under the Interfaces node and select Copy. Then in the target datasource, right-click the Interfaces node and select Paste.

or

Select one or more interfaces in the source datasource, then press the <Ctrl> key and drag them onto the Interfaces node into the target datasource. (If you do not press the <Ctrl> key, the selected interface(s) will be moved instead of copied.)