[{name:"John Doe",actions:["action1","action2","action3","action4"]},{name:"Margie Addams",actions:["action1","action2","action4","action3"]},{name:"Fer Doughnut",actions:["action1","action4","action3","action2"]},{name:"Anthony Peralta",actions:["action1","action2","action3","action4"]},{name:"Pete Parker",actions:["action1","action2","action3","action4"]},{name:"Josh Dean",actions:["action4","action2","action3","action1"]}]

db.collection.aggregate([{$addFields:{actions:{$slice:["$actions",{$indexOfArray:["$actions","action4"]}]}}}])