Switch validates property values to ensure that meaningful values are provided (to the extent such validation is feasible). Invalid property values are indicated by adding an alert icon to the flow element's icon, and by coloring the property background in the Properties pane. For example, after adding and connecting an FTP receive flow element, the canvas and the Properties pane look like this:
The FTP server address and corresponding login information fields are empty, causing the alert icon to appear. (Switch provides meaningful default values for most properties, but it is not possible in this case).