To help with your videos and their layout, you have the option to lock assets on your scene canvas. Locking an asset prevents it from being moved until you unlock it.
To lock an asset:
Select the element you wish to lock.
Right-click the asset and select Lock from the menu drop down.
The asset is now locked and is shown with a 🔒 symbol.
To unlock an asset:
Right-click on your asset.
Click Unlock.