Status Bar Options
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Tools > Options > User Interface > Editor > Status Bar
Read-Only status matches file system, use this page to handle the Read-Only behavior in the Code Editor.
When this options is enabled (checked by default), the IDE checks the read-only attribute of the file on the file system. If the file is read-only, the file in the editor is opened in read-only mode and the read-only menu option is disabled.
When this option is disabled, you can change the read-only status in the Code Editor for any opened file.