Can I make the bar full width, add a background image, or add a link or underline? (Essential Countdown Timer app)

Full width

Supported. The bar is styled to use the full width of the page. The final width can still depend on your theme's layout, so check the live store.

Background image

Supported. Go to Design → Card, choose Image background, and select your image. You can also set an overlay colour and opacity.

Link

The title and subheading are plain text and cannot contain a link. Instead, set Call to action to Button or Make entire bar clickable. Then fill in Button text and Link under Content.

Underline

Not supported. The title, subheading, and button text have no underline setting.