Is it possible to create a Stack chart using aggregate (group / count) of columns?

[Aristotelis_T]

Hi, is it possible to create a Stack chart using aggregate (group / count) of columns?

Selecting Horizontal Histogram I have then the option to group aggregate via Count:

However, when selecting Row Series (Stack) chart type, there is no option to Group Aggregate. Furthermore, I can not see any of my columns in the drop-down…

I want to create this horizontal bars chart of Abandonments by month, but Stacked: i.e. composed of Justified (green) and Not Justified (red) abandonments.

I tried creating some helper columns in the google sheet to follow the example of Stacked Chart of the manual, however could not include them in the Row Series Stack chart above because it would not show any of my columns in the dropdown…

Help!

thanks