If you have a dashboard in Tableau with multiple sheets, you can hide all the sheets used by Right Clicking on the Dashboard name, Hide All Sheets. 

All the used sheets are ‘gone’ – or rather, hidden, to make managing the workbook a lot easier.

If you want to know where a sheet are being used (perhaps in several dashboards), you can right click on the Sheet name, and check the Used In.

I wish there also was a similar function on our data sources, right click and “Used In” -> to see which sheets/dashboards they were used in. If you try to remove one that’s being used, you do get a warning and the dialogue box gives you the name of what will be affected – but that doesn’t show all – if it’s used a lot.