In Chrome you can do:

1. Press F12 (fn + F12 if mac)
2. Go to 'Sources' tab
3. Go to 'Workspace' tab
4. From your localhost page, 'Add folder' to the wwwroot of your blazor app

This lets DevTools have access to your wwwroot folder meaning updates you make in your IDE is now linked to the browser. Caveat: you will need to refresh the page (F5 or cmd + R on mac) to see the changes, sometimes the browser caches the CSS so a hard refresh (CTRL + F5 if windows) (CMD + SHIFT + R on mac) is required.

Also works for any CSS isolation you may have in your Blazor application.