In the first screenshot you have one player holding two instruments.
Dorico assumes you mean the player will be switching from one instrument to the other, not playing both at once. In galley view you will see both staves and you write the music on the staff corresponding to each instrument. In page view, Dorico will show one staff and automatically generate the text to show when the instrument changes, plus any clef and transposition (key signature) changes required.
Probably what you wanted to do was create two players, each with one violin. Dorico will automatically number the players “1 and 2” for soloists or “I and II” for section players (the first and second violin sections in an orchestra).