Is there an address book feature that shows which sheets are shared to individuals with a universal “unshare" option?
SysAdmins on Team or Enterprise plans can download a Sheet Access Report for an individual user which will show you all the sheets shared to the user. To get this report, right click on the user in User Management and select Download User Access Report. Through this same menu, you can remove them from sharing on all sheets owned by members of the account by selecting Remove User Sharing Access.
I didn't realize until today that the Sheet Access Report will show all users, whether or not you have them listed in the User Management or My Smartsheet Contacts - or nowhere at all except in the sharing tab.
I just cleaned up the access on all of our sheets/reports!