Showing multiple elements in matrix cells

I'm fairly new to PowerBI and I'm confused about how to do some data manipulation on PowerBI Desktop.

I have a table I imported from excel that looks like this (simplified example):

and I want to show it like this:

I have tried a few things. At first it looked like the matrix visualization would work but when there are multiple elements in the same cell, it only shows the first, last or the count of elements:

Then I tried pivoting the table to make it look exactly how I wanted before the visualization, but it throws an error when I select "don't aggregate" in the pivot option, as the element are lists and not text.

Any advice on how I should proceed to accomplish this?

Thank in advance