One card per scene, in order, with the structure headings between them. It is the corkboard, and it is the script — not a copy of it.
In most tools the index cards are a separate thing that has to be kept in step with the screenplay, and eventually is not. Here a card is a scene: the heading on the card is the slugline in the script, and the synopsis on it is the synopsis line beneath that slugline.
Move a card and you have moved the scene. There is nothing to synchronise, and nothing that can fall out of step, because there is only one copy of everything.
Drag on the empty board — not on a card — to draw a box, and every card it touches is picked out. Ctrl-click (Cmd on a Mac) or Shift-click adds one to the selection or takes it out. Then drag any of them by its grip and the whole group travels.
They land together, in the order they already read in — not scattered back into the gaps they came from. You selected them to make them a group, so they arrive as one.
Dragging a card that is not in the selection moves just that card and forgets the selection, so a group you picked out and then thought better of cannot follow you around. Clicking empty board clears it too, and one undo takes back the whole move rather than unpicking it scene by scene.
What you cannot do here is write the scene. Action and dialogue belong on the page, and a card that grew into a text editor would just be a worse one.
Along the foot of each card is its measure: the scene's word count on the left, and on the right the page — or range of pages — it falls on in the finished script. Both come from the same pagination the PDF uses, and both renumber the moment you move a scene, so the board always agrees with the page.
A scene that is in the wrong place costs almost nothing to move while it is one line of heading and one line of synopsis. The same scene, written out, costs an afternoon and a lot of reluctance.
That is the whole argument for outlining, and it is why the board sits between the structure and the page rather than off to one side.
The left-hand panel has three tabs: Projects, Outline and Cast. The Outline tab lists every section heading and every scene, indented by depth, and clicking one jumps the script to it.
It is the same material as the card board, in a narrow column that stays beside you while you write. Use the board to rearrange; use the panel to navigate.
The number down the left margin of the script is the scene's position, counted from the top — not a label attached to the scene. Move a scene and the numbers renumber, because in a draft that is what you want.
Locked scene numbers, the kind a production uses so that scene 42 stays scene 42 through every revision, are a shooting-script concern rather than a writing one. They are not in the app.