How do I add tiles to allow for added shortcuts?

You can edit browser.newtabpage.pinned in about:config and add ",null" to the list between the brackets: [....,null,null,null] The value null acts as a placeholder for history visits and you should be able to edit such a tile.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

If you close and restart Firefox then you should get the extra tiles. If not then use {"url":"about:blank?1"},{"url":"about:blank?2"},{"url":"about:blank?3"} instead of null,null,null

Thanks. Tried both solutions offered, neither solved the problem. Still 3 empty spots in the fourth row and no option to add shortcut. Also tried moving existing shortcut tile to spots, would not allow.

I also discovered that if I unpin my current shortcuts the spot goes away. This is what happened originally as there were two open spots, I unpinned a saved shortcut, and the tile went away. Now I have 3 spots and I do not want to try it again as I do not want to lose another shortcut..

Do you see the three dots if you hover a tile and edit such a tile? Add a Shortcut:

• https://support.mozilla.org/en-US/kb/customize-your-new-tab-page

Do you see null entries in the value of browser.newtabpage.pinned => websites pinned in about:config?

I had this problem, too. I had two rows of shortcuts and wanted to remove one shortcut in order to add a different one. Rather than editing the old one, I deleted it -- and had no empty tile to add the new shortcut. None of the solutions offered above worked for me. Here's how I solved it:

• opened 'Settings'
• opened 'Home'
• scrolled to 'Shortcuts'
• changed '2 rows' to '3 rows'
• restarted Firefox
• I now have two available '+ add new shortcut' tiles, one in 2nd row, another in 3rd row (which I'm not going to use, but it doesn't bother me)