Creating a new branch will create an Unknown output task in that branch. See Adding Branches.
Using Branch From Here... will create an Unknown output task below that branch. See Adding Branches.
Opening a configuration that contains additional plugins that are not installed on that system will cause these plugins to be replaced by Unknown tasks. Installing the additional plugins and re-opening the configuration will restore the plugins and their properties.
Opening a configuration that contains plugins only available in PlanetPress Workflow (such as Create PDF) from a PlanetPress Watch installation will cause these plugins to be replaced by Unknown tasks. Opening the configuration in a PlanetPress Production or Office installation or upgrading PlanetPress Watch to PlanetPress Workflow and re-opening the configuration will restore the plugins and their properties.