User context:
In complex use cases (therapeutic, creative, technical…), a long conversation may naturally branch into multiple themes.
The absence of a splitting tool makes it difficult to extract relevant segments, navigate historical threads, or reuse targeted content.
Proposed feature: “Split here”
Interface:
• Add a button to the interface: 
Split conversation.
• Clicking the button displays an interactive horizontal line in the chat history.
• The user drags this line to the desired split point.
• Upon releasing the mouse, a popup appears:
Split here ? (Yes / No)
Action:
• If “Yes”: the conversation is cut into two segments.
The cut segment (from this point onward) can be:
- Saved as a new conversation,
- or moved to an existing project.
• If “No” : Cancellation without consequence.
Important:
• No automatic duplication.
• No complex cross-project linking.
• The operation is manual, controlled, and simple.
Benefits:
• Better handling of long, multi-purpose conversations.
• Clean separation of clinical / emotional / creative usage.
• Provides more control for advanced users.
• Integrates seamlessly with the existing interface.
I hope my suggestion will be useful to you.