Reduce navbar min-height without modifying or adding css files

Question

I have successfully installed and configured Drupal 8
I am using bootstrap project as theme
The height of the navigation region on the top is as default has a css navbar which has min-height 50px as default value

it is possible to override this without changing the css files

Answer 1

As per your question, if I understood correctly, you don't want to modify CSS files
If you don't want to manually add or change a CSS file inside the theme folder

you can use Drupal Asset Injector and type the CSS with the editor provided in the plugin

Answer 2

The best way to work using bootstrap theme is by creating a subtheme. In the subtheme, you can update the variables or overwrite the navbar min-height, but if you really don't want to change any css/scss at all, you can do it using JavaScript (not recommended).

Something like:

(function ($) {
  $(document).ready(function () {
    $('ul.navbar').css('min-height', '20px');
  });
})(jQuery);