Hi Klaus, I love all your contributions in the SciFi section of alles-ebook!
You can add the "embed metadata" button manually to the toolbar:
Go to preferences, in the interface section choose "Toolbars & menus", choose the main toolbar (or any other option you prefer). Now you can add selected options to the toolbar, e.g. "embed metadata".
For some reason not all metadata are embedded during the transfer, so I always carry out these steps:
1. convert epub to epub
2. mark the specific files, click "embed metadata"
3. copy the files to my IP3 (via Calibre or file browser)