Hunt the window border in Cursor Dark Theme

Here I am editing a couple of files in two columns.

I am using the Cursor Dark theme

I want to adjust the window size by grabbing the vertical separator between the two columns.

I’m on a 4k Monitor. The hit zone is about 3 pixels

Here’s a screen grab

The redline at the bottom might be where it is, who knows. I have to hunt about until I can manage to stop the mouse in the magic darkness.