On my finale 25 on windows 10, I’m trying to score a piano trio for 6 hands. This includes 3 different grand staffs labeled piano 1, piano 2, piano 3. I have no problem creating this and only need to extend the left barline  (first barline) vertically to join this group. I can adjust brace but not that first barline. I can move any other other barline in the score. 
please advise. Step by step. I’ll attach a pic of a score that I’m trying to imitate. Why is this so difficult??