Top N Rows for Pivot Table [ID-40]

I would like to apply row limit to the rows in the pivot table, not the query that feeds the pivot table:

If I want to build a pivot table that only shows the top 20 rows but has many columns, I don’t think that there is a way to do that right now. The limit rows feature is applied to the query that pulls the data before it is pivoted, so it really means that I am limiting the output to 20 values (when i choose one metric). This makes it difficult to build dashboards around features for the top N shows.

Describe the solution you'd like
I would like to have a control in Explore to limit table result to a certain number. Since this control is not affecting the query, it makes more sense to have customize tab(?)

But what if metrics is applied on ROW? How do we decide top N row in what column?