Hi, 

The feature request is implemented and can be tested in version 6.4.0-develop.2.

The new message properties are dropFileHere and selectSingle. Here is a runnable example in which the requested functioanlity can be tested.

Regards,
Petar
Progress Telerik

Hello, Christian. 

Just in case someone wants to implement the same functionality as the one requested in the current item before the Feature request is implemented, below I will share the workaround we suggested in our private communication. 

This StackBlitz example demonstrates an approach that can be used as a temporary solution to change the text inside the Upload, based on the value passed to the multiple property. 

The example uses the following created method definition that dynamically changes the text inside the Upload component. 

created() {
    const bgMessages = this.multiple
      ? {
          upload: {
            select: 'Select files...',
          },
        }
      : {
          upload: {
            select: 'Select file...',
          },
        };
    loadMessages(bgMessages, 'bg-BG');
}

Regards,
Petar
Progress Telerik