Binocular - Double Ellipse in a single ellipse node

Can anyone explain how this is being done? I have looked to see if an expression is being used (right-click the "Center" attribute in the inspector for the ellipse node), and I just can't figure out the trick that is being used for this node.

If I drag a new ellipse node, then I can't duplicate this effect. Also, if I copy and paste the existing ellipse node, the double ellipse modality is lost.

Without seeing the nodes it's difficult to see what's being done.
The thing you're working with is quite bad practice though.
Masks aren't 'supposed' to be used as images.
But what appears to be happening is that there's an expression on the merge tool that's connected to the center of the merge tool. So if you move the ellipse, the center control of the merge moves the opposite way. The 'proper' way of doing this would be to just add two ellipse masks in line with each other and add the expression to the second ellipse node and then use that resulting mask to mask out a background etc

Can anyone explain how this is being done? I have looked to see if an expression is being used (right-click the "Center" attribute in the inspector for the ellipse node), and I just can't figure out the trick that is being used for this node.

If I drag a new ellipse node, then I can't duplicate this effect. Also, if I copy and paste the existing ellipse node, the double ellipse modality is lost.

i think you connected one input to mask input so the other ellipse is not showing . Disconnect the input from the blue input(mask input) and connect it to the green input (foreground input) then double ellipse will work

He is using the built-in Binoculars Effect in the Edit page Fusion Effects. The Ellipse is connected to both the Background and Foreground inputs of a Merge node and the Flip Horizontal button is enabled, which is flipping the Foreground input, so the Ellipse is mirrored. If you move the center of the Ellipse both copies move in opposite directions.

He is using the built-in Binoculars Effect in the Edit page Fusion Effects. The Ellipse is connected to both the Background and Foreground inputs of a Merge node and the Flip Horizontal button is enabled, which is flipping the Foreground input, so the Ellipse is mirrored. If you move the center of the Ellipse both copies move in opposite directions.

Yes!! That's it! Thanks so much Xunile. I hate not knowing how an effect is working.

You're welcome.