The Flutter Layout Explorer helps you to better understand
Flutter layouts.

For an overview of what you can do with this tool, see
the Flutter Explorer video:

You might also find the following step-by-step article useful:

How to debug layout issues with the Flutter Inspector

Using the Layout Explorer

From the Flutter Inspector, select a widget. The Layout Explorer
supports both flex layouts and fixed size layouts, and has
specific tooling for both kinds.

Flex layouts

When you select a flex widget (for example, Row, Column, Flex)
or a direct child of a flex widget, the flex layout tool will
appear in the Layout Explorer.