I am unable to add an extra entry to the directory that I am reviewing.

You will do the following to add entries:

Click on this icon on the toolbar.

When this box appears, select the number of entries desired and where they will be placed. Your defaults are 1 and After the last entry.

You can add up to 99 entries at a time, so if you need 100 after the last entry, you'll have to do this twice.