Is there a way to quickly identify all pending webhints?
Webhints cannot be searched in any way. RM displays WebHints only for people in the main view that you have on the screen. People View does not support WebHints. For Descendant View, I should say that RM displays WebHints for everybody in the view, not just the ones that are on the screen. For that reason, it can take a while for a large Descendant View to be displayed when WebHints are enabled.
WebHints are not stored in RM's database in any way, shape, form, or fashion. RM only knows to display WebHints only by sending queries to FamilySearch Family Tree and to myheritage.com. That's why there can be a delay between the time you first display a person and when a light bulb lights up for them.
Even the fact of whether WebHints have been confirmed or not is not stored in RM's database. Confirmations are store only on the FamilySearch Family Tree servers and on the myheritage.com servers.