How to show a colum total in a Power BI matrix visualisation that has implicit columns based on values?

I have a matrix visualisation in Power BI. I dragged a date field to the rows section. I dragged nothing to the columns section. I dragged three amount fields to the values section.

the matrix visualisation on the page shows a matrix with

column 1 : the date field

column 2 : the first amount field

column 3 : the second amount field

column 4 : the third amount field

in other words, Power BI shows the fields from the values section as columns. great!

How can I easily show a total for each row? Power BI ignores the setting to show column totals, because I dragged nothing to the columns section.....

The Matrix visual will only total the same metric, and in your case you have three different metrics in the Values well.

There are several solutions - below is the proper solution, the others solutions like using visual calculations or creating a measure to sum the three amounts will not display as Total in the matrix.

Proper (native visual) total
Create a new table in your model for the columns of the matrix.
As an example table named Dim Amount

Then create a Measure similar to:

Amount w/ Dim =
  var amtA = SUM(YourTable[Your first Amount column])
  var amtB = SUM(YourTable[Your second Amount column])
  var amtC = SUM(YourTable[Your third Amount column])
  return
    SWITCH(
      SELECTEDVALUE('Dim Amount'[Amount type]),
      "Amount A", amtA,
      "Amount B", amtB,
      "Amount C", amtC,
      amtA + amtB + amtC
    )

Now in your Matrix, add this new measure to your Values and 'Dim Amount'[Amount type] to your columns.
(FYI, if you add Date in rows, then add Amount type to columns without the measure in Values, you will get a visual error saying it can't determine relationship... Not to worry, as soon as you add the measure to the Values this is will all be good.)

There is another option but it requires modifying your model to unpivot those three columns. For example, going from:

To:

This can be done via Power Query relatively easily.