The UI Language determines the language used for dialogs and messages. By default, the Windows locale is used. If that is not supported, the fallback is English.
Currently, localisation exists for English, German and Spanish.
The UI Theme is just there for a bit of fun. You can change the colours and icons used in the application. Some examples are provided, but you can also create your own. In the program installation, you'll find a folder called Themes. There's an xml file controlling each theme, and you can add new folders and play with the colours and icons as much as you like. The file format should be reasonably self-explanatory.
By default, when you drop a file and all fields are automatically determined, conversion starts immediately. There are various reasons though, why you may want to see the dialog even though everything is defined:
In that case, check the Always show field selection dialog check box.The field definition dialog will always be displayed, showing all fields, not just unknown ones.
Settings file equivalents
Created with the Personal Edition of HelpNDoc: Free EPub and documentation generator