Suggestion: Warning when changing an external file

(as a new user) I would suggest a warning if the user attempts to modify a file that has not been "Imported" - especially "System" files.

This would reduce errors encountered by others using shared code that was unexpectidly modified.

To allow for shared "external" code that is expected to be modified perhaps there would be a "remember this setting" checkbox" on the dialog that warns that you are modifying an external file.