Gridbox & Forms

Hi! I use Gridbox & Forms. I created a form in a lightbox and want it to be displayed when clicking on a button from the slider. I copied the "embed code" and paste it into the appropriate field at the button, but it doesn't work.
I know it would work if I put it in the class name, but there is no such possibility.
But for something, there is this "embed code" field...

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