1. When an HTML element on your page has display: flex or display: inline-flex applied to it, you can see a flex badge next to it in the Elements panel.
2. In the Styles pane, you can see the flexbox editor button next to the display: flex declaration.
3. Click on it to open the flexbox editor. The editor displays a list of flexbox properties. Each property's value options are displayed as icon buttons.

[1] "Inspect and Debug CSS Flexbox layouts" - Chrome Developers