Hello Amy,
I believe drag and drop is not implemented for WebListBox in 2019. My memory is foggy on it, but I do recall it working at some point prior to the 2019 releases.
That said, you can implement it using container controls. Please review this post from last year by John Scanlon, web container drag and drop with all properties, the example file is still accessible (just note Greg’s fix to a couple of lines of code noted in the post).
I had hoped Row to Row or Cell to Cell drag and drop would be a feature of the new WebListBox. Most of my web apps are data centric and this would be handy without complex workarounds.
I hope that helps. Kind regards, Andrew