Expand/Collapse node in TreeByKeyTableColumn UI Element

Hello Experts,

I have created a method to fill the tree hierarchy (TreeByKeyTableColumn UI element)

When I click on the triangle(or arrow) mark at the beginning of every line item, the node expands or collapses.

Additionally, whenever I click on the empty space that comes before the arrow mark, the node expands or collapses.

But, when I click anywhere after the arrow mark on the line, the node doesn't expand or collapse.

How do I enable this?

Thank you.

Vijay