WordPress Appearance Editor Menu Option is Missing. I recently encountered an issue where the option to edit my theme files from the WordPress back end was gone. My WordPress Appearance Editor Missing – Gone! As it turns out, a setting within the iThemes Security was the culprit. Fortunately the fix was simple, and I was back up and running again within a couple of minutes. But, figured I'd quickly share the fix in case others encounter the same issue.
How I fixed the Missing WordPress Appearance > Editor option
Login to WordPress back end.
From the sidebar, navigate to Security > Settings
From the iThemes Security Settings Page, navigate to WordPress Tweaks and Click Configure Settings
Scroll down to the File Editor and uncheck the option. Then Click Save Settings
Now go back to the sidebar and navigate to Appearance and the Editor should be available.