Dependency

You already speak in dependencies. "Build starts when design is done." "QA comes after build." "Photos can happen during build." Every ordering word — then, once, after, while — is a dependency, said out loud. Writing a plan is mostly writing those words down; drawing a chart is mostly turning them into arrows.

Dependencies are the ingredient people skip, and the one that makes a timeline worth reading. A chart where every bar starts on day one isn't a plan, it's a wish — if nothing is waiting on anything else, you haven't finished thinking about the work. The most common flavor by far is finish-to-start: A finishes, then B starts.

The failure mode in the other direction is over-linking: connecting everything to everything until the chart is spaghetti and every small slip triggers an avalanche of recalculated dates. Record the constraints that are physically or logically real — the ones where B genuinely cannot proceed without A — and let mere preferences stay out of the diagram.