Fill in not existing values

Hi AlB ,

thank you for your reply. I took a look into the thread and luckily it pointed me to a possible solution, although not with DAX. 

let
    Source = Tasks,
    #"Pivoted Column" = Table.Pivot(Source, List.Distinct(Source[TaskName]), "TaskName", "Person"),
    #"Replaced Value" = Table.TransformColumns(#"Pivoted Column",{},(x) => Replacer.ReplaceValue(x,null,"not scheduled")),
    #"Unpivoted Columns" = Table.UnpivotOtherColumns(#"Replaced Value", {"TaskDate"}, "Task", "Person"),
    #"Changed Type" = Table.TransformColumnTypes(#"Unpivoted Columns",{{"Person", type text}, {"TaskDate", type date}})
in
    #"Changed Type"

Source:

First I pivot on the taskName column so that all the task rows get pivoted into columns. As value I take person and as aggregate function 'Don't aggregate'. This creates nulls where no task is scheduled.

Next I replace all nulls with my custom text (eg 'not scheduled') with

Table.TransformColumns(#"Pivoted Column",{},(x) => Replacer.ReplaceValue(x,null,"not scheduled"))

Then I unpivot TaskA and TaskB so that I get my Task and Person columns back. but this time with my added values.

This creates my desired output, unfortunately not with dax, but at least I did not have to enter the values in the database.

Result: