https://developer.mozilla.org/en-US/docs/Tools/Page_Inspector/How_to/Examine_Flexbox_layouts

fond size
about:config
devtools.toolbox.zoomValue 
    set more than 1
or just use C-+

2025
CoderCoder - How to debug CSS with Firefox Developer Tools 0:00 of 41:49
    https://www.youtube.com/watch?v=AR9Em0X-N_8
2021
https://mozilladevelopers.github.io/playground/debugger/04-conditional-breakpoints/
    https://habr.com/ru/post/592095/
https://mozilladevelopers.github.io/playground/debugger/03-the-call-stack/
    https://habr.com/ru/post/588981/
https://mozilladevelopers.github.io/playground/debugger/02-check-variable-values/
    https://habr.com/ru/post/587516/
https://mozilladevelopers.github.io/playground/debugger/
    https://habr.com/ru/post/586776/
https://www.smashingmagazine.com/2021/02/useful-chrome-firefox-devtools-tips-shortcuts/
2019
https://hacks.mozilla.org/2019/09/debugging-typescript-in-firefox-devtools/
https://nicolaschevobbe.com/2019/01/17/webconsole-2018-retrospective.html
https://hacks.mozilla.org/2019/01/designing-the-flexbox-inspector/
2018
https://www.sitepoint.com/performance-auditing-a-firefox-developer-tools-deep-dive/
https://hackernoon.com/10-firefox-dev-tools-tricks-that-will-blow-your-mind-d641f1714903
https://hacks.mozilla.org/2018/05/debugging-modern-web-applications/