DAX: sum with filters

Build the column as you would if the row only exists one time. Then, when pulling it into PowerBi visualizations, use the portfolio/isin/ column labels as your axis or row on the matrix. Just use the column headings instead of the cell references you would in excel. You may initially get an error about no row reference existing but, often times, this is overcome when you add it to the visualization.

Unfortunately, I am not able to see the images you are sharing today as I am on my mobile but the gist of what I am reading is that you want a specific column calculation that can be combined based on the portfolio. The visualization rows/axis will handle that part.