Changing / Swapping Data-source for Duplicated Worksheet

    How to set up  worksheets which I can re-use with different filtered data /data source ?

1. Copy the Tableau file (or save as different name). Now you have FileA and FileB.
2. Open up FileB and replace data source with your new datasource. 
3. When that is done, open up FileA and Copy/Paste the workbooks/dashboards you want from FileB to FileA. 
4. These should now have the new datasource and FileA still has the original datasource. Keep going for as many datasources as you have.