You can easily replace any video clip in your project while keeping all of the existing connections and overlays intact.
Click and hold on to the new clip and drag it over the old clip.
You'll see the old clip turn purple and then you can release the new one. Then you'll be asked if you want to replace the old clip with the new clip.
When you tap Yes, the new clip will replace the old one with all the connections and overlays in place.
Once you hit the blue Publish & Update button, everywhere your adventr is shared will automatically be updated with the new clip.