Safe & Quick Hide Files and Folders (SQHideFile)
From Just Solve the File Format Problem
Safe & Quick Hide Files and Folders (SQHideFile) by Microidea Software Studio secretly appends files to the end of other files.
This feature is called 'Camouflage' and 'Decamouflage'
The same basic program appears to have been reskinned as Secure Box
The reviewed version simply puts all the files to be hidden in a ZIP and appends it to the host file. Perhaps later versions do more.