Webpage Thumbnails

I am a fairly new user to Chromodo and have been happy with it so far.

Last week, I clicked on (actually, “fingered” might be more accurate since it was touchscreen) a thumbnail and accidentally deleted it. Since the “undo” option appears below the area that was visible, I did not see it. I eventually got that thumbnail back by visiting the site repeatedly, but then fat-fingered it away again.

In Google Chrome, the “Restore All” option brings them all back when you make this mistake. I have tried deleting other thumbnails and clicking on “Restore All” to no avail. I now have no thumbnails remaining.

How do I get these back? If I delete Chromodo and re-install will it start populating them again? Is there some extension that will let me manage these (I could not find one).

I can live without them, but I had been getting used to going to some of my more frequented sites by using them.