go to the databsource tab and click show hidden values and then go to the any sheet and hidden dimensions or measures now will be pale color. Right click and unhide/show, i cant remember exact wording on options.
Thanks. But then I still need to go to each workbook to see which fields weren't used, right? Or will those that have a pale font, be hidden throughout the entire dashboard?
In fact those with pale fonts aren't used in your intire workbook not just in a particular dashboard.
Hope that was helpful.
I just wanted to check back with you if solution provided here answered your question or not. If it did, can you please mark as correct answer so that it is cleared from question board that needs to be answered as well as other users in future can benefit from it. If not, please feel free to ask for help. Thank you.
There is software called RapidDox that does auto documentation for Tableau Workbooks. One of the outputted documents is unused fields. Hope this helps!