Firefox Home shows only 8 shortcuts and hides the Add button

Firefox Home shows only 8 shortcuts and hides the Add button despite being set to 4 rows Environment: - Windows - Firefox 157.0 (64-bit) - The same issue occurred in Firefox 156.0.1 before updating. - Built-in Firefox Home is selected for the homepage and new tabs. Steps to reproduce in my current profile: 1. Enable Shortcuts in Firefox Home settings. 2. Set the number of shortcut rows to 4. 3. Add shortcuts using the "+" button. 4. Once 8 shortcuts have been added, the "+" button disappears. 5. Open another new tab or restart Firefox. Actual result: Only one row containing 8 shortcuts is displayed. There is no "+" button to add a ninth shortcut, although the settings still show 4 rows. Expected result: Firefox should allow additional shortcuts in the configured rows and keep an option to add more shortcuts until the available slots are filled. Checks and troubleshooting: - Confirmed that browser.newtabpage.activity-stream.topSitesRows is set to 4. - The issue also occurred in Troubleshoot Mode. - Temporarily enabling sponsored shortcuts did not help. - Updating from Firefox 156.0.1 to 157.0 did not help. - Testing browser.newtabpage.activity-stream.nova.enabled set to false did not help. Additional context: During earlier troubleshooting, browser.newtabpage.pinned was manually edited to add a ninth shortcut. After restarting Firefox, the previous shortcuts disappeared except for YouTube. I then rebuilt the shortcuts using the normal "+" button. The same problem returned as soon as I reached 8 shortcuts. The issue therefore existed before and after that manual edit. I have not tested with a separate, fresh Firefox profile. I do not know which Firefox version first introduced the issue.