Once you've added assets to the timeline, click the toggle next to "Transitions."
To select your "Transition Style" for this video, click the word "Transitions."
Hover over each style thumbnail to preview, click to select, then click "Apply."
You now have randomized transitions from your selected style on each asset.
Double-click any asset to see the specific randomized transition, then click the thumbnail to manually select a different transition. Choose "None" if you prefer no transition into this asset.
Click "Preview & Produce" to watch your video with transitions.