working-on.js

lets(
  /* Find all unfinished tasks */
  tasks, prop("Tasks").filter(current.prop("Status") != "Done"),
  
  /* Find all the people assigned to those tasks */
  people, 
  tasks
    .map(current.prop("Assignee"))
    /** 
     * Because Assignee is a Person property, it's a list, 
     * so we have to flatten this list of lists, make it unique, and sort.
     */
    .flat()
    .unique()
    .sort(),
  
  /* Finally we build a list of "assignments" */
  assignments,
  people.map(
    /**
     * For each person, we're going to find any related unfinished tasks assigned to them.
     * We need to set an alias called "person" because we'll need to use nested "current"s here
     */
    let(person, current,
      /* Output the person's name and concat a string... */
      person + " is working on\n" +
      
      /* Find all their tasks, sort them... */
      tasks
        .filter(current.prop("Assignee").includes(person))
        .sort()
        /* Then for each of them return the name of the task with a tab character in front of it */
        .map("\t" + current)
        /* Join all the tasks together with a newline */
        .join("\n")
    )
  ),
  
  /* Add double newlines between users */
  assignments.join("\n\n")
)