Matrix - Add a Row from another table

EstherBR Here is an example that more or less aligns with what you are trying to do:

Create a table called "Categories":

Set the Sort column to be the Sort by column for Category.

Now create the following measure for use in your Matrix:

My Measure =
VAR _Category = MAX( 'Categories'[Category] )
VAR _Return =
  IF(
    _Category = "Total Segment",
    SUM( 'Cities'[Sales] )
    CALCULATE( SUM( 'Cities'[Sales] ), FILTER( 'Fact Table', [City] = _Category ) )
  )
RETURN _Return

Put the Category column from your Categories table as the rows to your matrix and My Measure as the Values.