Widgets require a player viewport which doesn’t exist at the edit time (so they couldn’t be previewed either). This is why it requires the game to be running.
Thanks–that got me on the right track. In the end, turns out, if I start playing the level before I start playing the cinematic, the widget shows up. Not sure why the game needs to be running for the widget to show up over the cinematic, but it seems to work and exporting the video also includes the widget, so I think I’m all set. Thank you for responding!