Click on the “three dots” on a thumbnail, this will open a menu like this:
Click on “Add transition” to add the transition in between the selected scene and the next scene.
Clicking on “Add to all scenes” will add the transition to all scenes, except for Intro and Outro.
Remove Transitions
Select a scene that already has transition and click on the “three dots” menu. like this you can remove the transition from this scene or from all the scenes.