This is the area of the interface where you will be adding the different components and data sources that are required to run your analysis, and connecting them in order to define each step of the workflow in order of execution.
In this central panel you will always find the main diagram of your workflow, with all its components and data sources connected according to what you have established.
Additionally, in the canvas you also have the possibility to add visual assets and annotations to provide explanations on your workflow. You can do it by clicking on the corresponding icon in the toolbar (located just below the blue header, in the upper middle of the screen) and drawing it directly with your mouse on the canvas. This will help you make very complex workflows more understandable.