New feature was introduced in Photo Database 4.5 - new virtual directory "Collection", that includes special directory "Duplicates". Full path: "Mu Compures > Collection > Duplicates". Open this directory to see all duplicate pictures in collection, program automatically scan all collection for pictures with duplicate content.
You can use quick navigation to open directory with selected picture (see at the bottom in the picture below).
To remove duplicates just select unnecessary pictures in explorer (use buttons Ctrl and Shift for multi-selection) and press remove button (button Delete). All selected pictures will be deleted to recycle bin including incormation in collection.
For automatic removing information from collection directory with picture should be synchronized with current collection in collection settings.