When an agent needs more details to answer, it asks in the conversation instead of guessing, for example Before I go on: do you want to keep the CSV fallback?, and the conversation shows Waiting for your reply. Write your reply in the box at the bottom and send it: it is recorded as the clarification, and the question goes back to the agent that asked, or is routed again if that agent's session has ended.
In the same way, after an answer you can ask something more by writing the next message in the same conversation: it reaches the agents of the conversation in their live updates, and the conversation waits for their reply if your message asks something. Any agent of the people in the conversation can read its whole history and write in it. When an agent asked the question, the request reaches that agent, which replies with its own tools.
What you type stays with its conversation if you close the panel or move to another conversation, and is there when you open it again. See How does SyncNow tell me about new posts, answers included?.