You can drag the bookmark onto the page from the Library dialog (CTrl+Shift+b). This article has the steps: Customize your Firefox New Tab page -- see the Add a Site section.

Does that work? If not, where are you running into a problem?

opened the show all bookmarks link, tried to drag the short cut to the "most visited" folder, does not work. What am I doing wrong; any other ideas.

Hi bennett9, I think the Most Visited folder (blue icon) is generated using a search and can't be modified manually.

Did you try dragging the bookmark onto a new tab screen? Since that requires resizing windows, actually, it would be easier to drag from the Bookmarks Sidebar (Ctrl+b opens and closes the sidebar). Apologies for not thinking of that earlier.

I can drag the bookmark into any other folder on my list but still won't drag to the most visited one.

Sorry, I was confused. I thought you wanted to add a bookmarked site in place of one of the 9 thumbnails on the New Tab page (the page that appear when you press Ctrl+t or click the "+" button at the end of the tab bar).

The Most Visited "smart folder" (blue icon with the magnifying glass) is generated by a search of your history. It isn't a regular bookmark folder that you can freely modify.

Would it work to create your own new folder of your most regularly used bookmarks instead?