We are setting up one Kanban board and one Sprint in one project that uses one workflow. The input is the backlog. The backlog for Kanban is new input, and for the sprint the issues that were finalized in Kanban.
The issues finalized in Kanban need to be in the backlog for the Sprint as there they will be selected to pick up in the current sprint. We cannot have all issues automatically being addressed "To do" in the Sprint and also do not want to see all Kanban issues in the Sprint backlog.