My guess is you are on a newer version of GP. The menu format was changed and the Delete and Insert are not available in this new layout. What you will need to do is change the layout to Menu Bar, close and restart GP. You should then have the option to insert a row.
Change Window Command Display.
Microsoft Dynamics GP | User Preferences.
For window Command Display, change it to Menu Bar.
Log out of GP and Back in.
Now in the AFA report, you should have the Edit on the Ribbon you can use to add a row.
I hope this helps!
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