If you want users to be able to save their preferences within the Work Dashboard tab, you need to set the permissions appropriately for a couple of attributes in the Identity Vault. Specifically, if you want users to be able to save customizations associated with the Customize, Filter, and Rows actions (actions which allow control the display of data on several sections of the Work Dashboard), or change the sort of the data displayed, you need to ensure that the permissions on the srvprvUserPrefs and srvprvQueryList attributes are set so that the user is able to write to these attributes.