You can increase/decrease font size within chrome's developer toolbox by pressing CMD and + or - but it seems only to work in docked mode.
If I do that within an undocked separate window, it zooms in/out the web page too.
Is there a possibility to achieve the same in floating-window-mode?
EDIT: See related bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1100135