Children are placed top to bottom, each as tall as it measures. Flexible children (plots without a height, [bb_spacer()] without a height) share the height left over when the stack is given more room than its content needs, as the body of a [bb_page()] is. A stack with flexible children is itself flexible.
Examples
bb_stack("Title", "Body text", gap = unit(6, "pt"))
#> <bb_stack>