Lost values after Grouping to Matrix

I’m new to Grafana so maybe I just misunderstand something but I’ve got a problem.
I want to create a matrix using 3 types of values (x,y,z).
I am using Grouping to Matrix transformation and I’m using x for Column, y for Row and z for Cell value. In my scenario I have multiple z for the same x and y ex:
|Column 1 | Column 2 | Column 3 | Column 4|

|— | — | — |
|x1 | y1 | z1 |
|x1 | y1 | z2 |
|x1 | y1 | z3 |

But in the matrix for x1 and y1 only one z value (most recent) is shown.
|column/row | y1|
|x1 | z1|
I would like to have in the cell for x1 an y1 shown z1 z2 and z3 values.
|column/row | y1|
|x1 | z1,z2,z3|
is it possible and if so how?