How do i style the bottom-right corner of a ScrollArea?

[Nyte]

scrollarea.jpg

How do i style this white square in a scroll area?

I was looking for something similar to the way you style the corner of a table

QTableView QTableCornerButton::section {
     background: red;
     border: 2px outset red;
 }

QTableView QTableCornerButton::section {
     background: red;
     border: 2px outset red;
 }

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But i can't find the name of the selector or psuedo-class for this item.