I use Google Chrome, and utilise the "New Tab page".
This claims to show "Thumbnails of the websites that you visit frequently" (although it does not explain how this is determined) and has options "to remove a most visited site", but does not seem to have any option to add sites.
I have recently returned from a long trip, and the list contained lots of sites I no longer need, which I deleted, but many of my sites have fallen off.
At one stage I saw a Restore All but can't seem to reproduce this. Is there any way to manage which sites show.