When we extract data it will ask to hide all unused fields, once selected all used fields only shown in extracted data window.
click dimension in data window and hide.
You can hide unused fields as shown in GIF animation below.
You can also show hidden fields. These are shown in gray color.
You can unhide individual fields by choosing unhide (right click option).
you can unhide multiple fields by selecting many and choose unhide (right click option).
It would be nice if this could be done in a single step as requested in Unhide All Hidden Fields.
I was looking for something that can be done from the dashboard as I have 20+ sheets and was trying to avoid having to go into every single one.
But this has been helpful.