Pass parameter to Member Signup Form

Hi, I’m trying to pass a parameter to a Member Signup Form. I’m following the documentation for the openLightbox() call on wix-window.
When I try to read the context in the lightbox (Member Signup Form), it is null.

$w.onReady( function () {
26  let received = wixWindow.lightbox.getContext();
27  $w('#lightBoxReceive1').text = received.pageSend1;
28  $w('#lightBoxReceive2').text = received.pageSend2;
29} );

The documentation says to
“make sure Automatically display lightbox on pages is set to No in the Lightbox Settings panel in the Editor”. But I can’t find the “Automatically display lightbox” option.
Is this available to Member Signup Form?
Thanks,
Tim

On the editor, go to the lightbox, select the lightbox element (by click), then click Set Triggers and continue from there.

Thanks J.D.
I’ve clicked all over the editor window and I only get options for the overlay (e.g. “Set up Overlay”) and the form (e.g. “Form Settings”).
This is what makes me wonder if a Member Signup Form is different than a regular Lightbox.
Thank,
Tim