Perhaps I'm missing something, but you can do this in the current matrix visual using drilldown. And, it's more powerful as you can drill down/up by levels, nodes, or, levels and nodes - by rows or by columns. It's just not as intuitive as having the "+" and "-" buttons next to each row.
Clicking on the drilldown arrow on the far right activates "cell" drilldown. With the arrow activated (dark), you can then click on a row cell header and it will drill down on just that cell to the next level. Click a cell again and it will go to the next level for just that cell. Pretty slick! Hope this helps.
I see what you mean. This can fix the problem already a little bit. Thanks!
Indeed not that user friendly and all the other "high levels" are not visible anymore, but OK for now
Thanks a lot!!