You'll find Overlay in the slide settings menu, above "Main Asset Styling."
With Overlay you can:
Add a second logo to a slide, alongside your theme logo.
Add an animated frame or effect on top of a slide, including one that moves beyond the slide's edges.
Create a transition-style effect between slides using an overlay asset.
Choose whether the overlay sits in front of or behind other slide elements, like the background or your logo.
Overlay gives you position, scale, opacity, and animation controls for the asset, along with timing controls for when it appears. Its position adjusts automatically when you switch between video formats, so it stays correctly placed.
Overlay adds one asset layer per slide. If you need more than one extra asset on the same slide, use a Layer Slide instead, which supports up to six.
How do I add an Overlay to a slide?
Click on the slide to open the slide settings menu.
Click "Overlay."
Add your asset, then adjust its position, scale, layering, and animation.