Having a notification that a secured folder that is by default locked, is still locked, is defunct. It is not necessary and is simply bloat on the notification screen.
There is a more serious issue also. It is an advertisement to anyone who views the phone that a file with sensitive data or information is present on the phone. This is something which I can foresee being an issue.
Based on what you have described, I suspect you're referring to a notification from Secure Folder that appears after you have restarted your device.
When your device is restarted, applications will need to initialise upon boot up in order to start receiving notifications and intialise other app functions. As there are applications that are present in Secure Folder, this notification prompts you to launch Secure Folder so that the apps are able to initialise.
This notification will appear until Secure Folder is launched. To avoid this notification, please make sure to launch Secure Folder when you restart your device and the notification will disappear.
Please let us know if you have any further trouble, or would like any clarification on your Secure Folder notification.
