I start by creating a lead, then I convert this lead to an opportunity. Then it appears in 'clients' and 'opportunity'. 

Once an opportunity is lost, I would like to remove it from the opportunities but I do want to save the details regarding this lost client somewhere. 

When I remove it from opportunities, it remains in 'clients', that does not make sense to me as the opportunity/client is lost. I rather have it in a separate folder 'lost clients' or have it back in my leads, for future contact. But if I want to do that, I have fill in the details about the client all over again.

There is probably a much simpler way of doing this, can anybody help me?