In order to improve Kanban for multiple warehouses, you need to follow the continuous improvement cycle, which consists of planning, doing, checking, and acting. When planning, you must identify a problem or opportunity for improvement and set a goal and plan to achieve it. For example, you may want to reduce your lead time by 10% or increase your fill rate by 5%. During the doing step, you must implement your plan and test its effectiveness. You can use various tools and techniques such as root cause analysis, kaizen, and 5S to improve your Kanban system. Root cause analysis is a method of finding the underlying cause of a problem and eliminating it. Kaizen is a philosophy of making small and incremental changes to your Kanban system and processes. Lastly, 5S is a framework of organizing your Kanban system and workspace which consists of five steps: sort, set in order, shine, standardize, and sustain. Finally, during the check step you must measure and evaluate the results of your plan and compare them with your goal and expectations. Lastly in the act step you must decide whether to adopt, adjust or abandon your plan based on your findings and feedback.