You can manually create a custom Gantt chart from scratch using the native Chart menu of PowerPoint. In its Chart menu, you can find several types of standard charts including line, bar, area, pie, ...

lends itself to charts that are less formal and less businesslike in nature. In fact, what you need in these cases is something more like an illustration than a chart. New chart features in PowerPoint ...

Firstly, consider the purpose of your diagram. Are you trying to show a process, illustrate a relationship, or compare data? Your goal will determine the type of diagram you choose, be it a flowchart, ...