We developed a creativity support tool called IdeaCrepe that manages the history of ideas using a layered structure. Handling ideas with a creativity support tool that is able to record history is very useful for understanding these ideas, the evolution of the ideas over time, and the relationships between the ideas. Looking back through the history of creative activity may contribute to the further development of ideas. In this research, we introduce a concept of "layered structure" based on a time series to manage the history. Using this structure, we can look back at past states of ideas, and examine their development. These features can manage the creation and modification of ideas.