Tnsnames editor is greyed out and you cannot edit it if users have limited system privileges (4269914)

In the Connection window, users cannot use the Tnsnames editor when a user has limited sys rights.
This is not a problem if the user has full Admin rights.

or

User cannot save tnsnames.ora using the Tnsnames editor.

The tnsnames.ora is an Oracle file and not specific to Toad.
Toad for Oracle is a GUI and if it cannot access the tnsnames.ora file, one will be denied to work with the tnsnames.ora file through the Toad Tnsnames editor.

WORKAROUND:

Determine if one can open the tnsnames.ora file as a Admin in Notepad by working around the privilege issue.

1. Right click on Notepad.
2. Select “Run as administrator” (might prompt for password).
3. Open and drill to tnsnames.ora file.
4. Determine if one can edit the file.
5. If one cannot still save this file, one will need to get in touch with their Help desk.

RESOLUTION: 

Grant privilege to read and write to this file specifically.