I strongly believe you're mixing up concepts, so I'll take some wild guesses here.
In Scrum, the tasks would be named sprints.
You may mean
In Scrum, the goals are defined per sprint.
Where the Sprint goal defines what is the value delivered within a given period of time. As Kanban doesn't have this period constraint, you'd like to know how to give visibility of this "intention of deliver value". In other words... your question may be
In Kanban, how can I socialise what we're intended to do for the next "period of time" if I don't have a Sprint goal anymore, as I had in Scrum?
Simply put, you don't. Scrum has one constraint to ensure team is focused, which is the Sprint. Kanban uses other types of constraints (WiP limit is the most known) to achieve a similar result. Kanban moves away from the idea of a "single unit of value" delivered over a period of weeks (i.e. Sprint Goal) into a system where you deliver small parts of the same value in an incremental & continuous fashion.
So, back to your example
Release 1 : Managing Clients.
------ [Task 1] : Add new client.
------ [Task 2] : Edit client info.
------ [Task 3] : Delete client.
What you want is to give visibility of the incremental work towards the completion of the "Managing Clients" delivery. There's a few ways of giving this visibility and it'll depend on the tools you're using. You may use a Swimlane per deliverable. Beneath this swimlane, you have all the incremental parts of it. As the items in this swimlane are completed, anyone can observe the progress towards its completion.