The version of Knime concerned are 3.5 and 3.6. When I open Knime I have sometimes an error : ERROR LoadWorkflowRunnable Status: Error: Node “Missing Value” not available from extension “KNIME Core” . But in fact the missing value node is present as in the attachment. I change my installation change disk where I installed Knime but it still appears. I noticed also thet when you want to drag the missing value node from the node repository it takes more time than for the other nodes.