Nesting can be especially useful when designing with
Auto Layout (flex containers), creating cards, galleries, and more. For example, you've created a card for your blog with a title, description, and image. You then grouped these elements (select multiple elements → Group), set it as an Object group (Group → Object), and enabled Auto Layout (Auto Layout → Flex → Auto) so the card's height automatically adjusts based on its content. You also added a URL and set a background color.
To more flexibly adjust the spacing between the title and description, you grouped these two text elements together and enabled Auto Layout for this new group. Now, you have a nested group with flex properties.