#2317193 | Port "Add an item to a list" action to D8

Initial port
Could you elaborate? I'm unsure as to what's the issue here - I am getting those values from the context in the lines just above what you're highlighting:

    $list = $this->getContextValue('list');
    $item = $this->getContextValue('item');
    $position = $this->getContextValue('pos');