Each theme has its own set of display options. For example, some themes let you show captions underneath a piece or overlaying it. Rather than going project by project, you can edit some project styles all at the same time.
- Click on the Design link.
- Scroll all the way down in the sidebar and click on Edit Project Defaults.
- Click the icons or toggle the switches to change to your desired style.
- Changes update immediately and boom, you're done.
This applies to the Pancake, Mason, Copybara, Lefty, and Thumbs theme.