It looks like this option was taken away in the 8.5 beta. While in the Gallery, you used to be able to select a photo or photos and have the option to send to the Secure Folder Gallery (the Secure Folder Gallery had an option to move out of Secure Folder, which would move it back the Gallery). This option seems to have been replaced with Move to Private Album (and no option available in the Secure Folder Gallery), which deletes it from everywhere.
Is Samsung going to gradually get rid of the Secure Folder?
If your secure folder is not visible, then you won't have the option to move it there. Once you make it visible then you see the option to move to whatever you have it called and the private folder.
