Short answer: You don't switch between an editor and a preview - in Forge, the Stage is the game, running the whole time you work. Click any event in the timeline and the stage shows exactly that moment. Click a dialogue line to rewrite it in place, or drag a character to reposition them. Edits apply on their own about half a second after you stop typing, the stage updates immediately, and Undo takes any change back. A Live / Paused toggle in the top bar lets you freeze the frame while you work.
The Stage is the real game
The editing canvas in Forge's default view is the same player your readers get - same textbox, same fonts, same effects, same everything. There is no build step and no reload. What you see while editing is what a reader will see, because it is literally the same running game.
Click a moment, see that moment
Click any event in the timeline - a line, a background change, even a silent step like setting a variable - and the playhead parks exactly there. The stage always renders precisely that moment, so you never replay through a scene to reach the line you want to change. More in How do I jump to a specific moment in my scene?.
Edit right on the frame
- Dialogue - click a line and type into the real textbox, with live formatting and the speaker control right above it. See How do I write dialogue directly on the stage?.
- Characters - grab a sprite on the stage and drag it where you want it. See How do I position a character?.
Every event also has an editor panel with all of its settings, opened by clicking the event in the timeline.
Changes apply themselves
There is no Save button. About half a second after you stop typing - or as soon as you press Enter or click away - the edit saves, and the stage updates immediately. If you change your mind, Undo steps back. The details are in Why is there no Save button in Forge?.
Freeze the frame while you work
The top bar has a Live / Paused toggle. Live plays your game normally as you edit. Paused freezes forward progression - clicks and timers stop advancing the story - so you can hold on one frame and take your time adjusting it. See What does the Live / Paused toggle do?.