How to hide repeated values in matrix

Hi  Anonymous, you can conditionally format "Values" section (highlighted in violet below).

The way to do it is by using INSCOPE() function, which checks whether a specific element of hierarchy is currently selected or not (use NOT INSCOPE() to flip around the behavior). Here is the example of DAX code:
 

Document Date = 
    IF( 
        ISINSCOPE( Table1[Column 1] ) && NOT ISINSCOPE( Table1[Column 2] ),
        SELECTEDVALUE( Table1[Column 3] ),
        BLANK()
    )

You can't yet apply conditional formatting to column/row headers (all levels will have the same selected colour).
I hope it helps! Good luck with your project 🙂 

Anonymous, in such case I stongly suggest you to take some online course on PowerBI. You need to have a basic understading of the tool (transformation with Power Query, data modelling, creation of measures with DAX and data visualization). PowerBI is a powerful tool, but requires knowledge of foundation to benefit from it.

Some of the things are not so immediate as they are in Excel. Unfortunately, the one you're asking about is one of them.

Take your time, learn the basics and read my answer once again. In case you'd have questions after, feel free to tag me again 😉 Good luck with your journey, you're on the right way!