Ohh, if this is the case then it kind of makes sense to store on the Task itself. Which means the Task object will have to store it, and then the UI will display it :(
I think the actual solution is a vault , per user, which would allow users to keep their credentials on the sever, the agent to pass those to the Task when it spins it, based on the user. Unfortunately the vault feature is only available on the paid/enterprise version ( with RBAC etc.).
Does that make sense?