dev tools freeze dom code example

Example: Freeze screen in chrome debugger

Got it working. Here was my procedure:
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1. Browse to the desired page

2. Open the dev console - F12 on Windows

3. Select the Sources tab in chrome inspector

4. In the web browser window, hover over the desired element to initiate the
popover

5. Hit F8 on Windows/Linux (or fn + F8 on macOS) while the popover is showing.
If you have clicked anywhere on the actual page F8 will do nothing. Your last
click needs to be somewhere in the inspector, like the sources tab.

6. Go to the Elements tab in inspector

7. Find your popover (it will be nested in the trigger element's HTML) 

Have fun modifying the CSS :)