Adding a field parameter fields to TopN visual filter pane

I have created a field parameter table as below:

I have used above field parameter in below visual x-axis:

Now its working well! But I want to filter this visual for TopN values as shown below based on parameter table fields column as shown below:

But when i drag this field parameter column in filter this visual pane 'By value' it shows First Parameter and it doesn't aggregate.

I am confused how to filter visual by the top 20 'Name' column by variance Field parameter fields column.

Can you please help us with this?

Thanks in advance!

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