You can replace the entire meta tag or it’s content. It’s not recommended to replace CSS class names as it might break the site. But if you need to replace them there’s a way around which needs a bit of coding skill.
If you want to replace css class name “wp-navbar” to something like “xyz-navbar”, then you’ll need to add following replacement in “replace in html”:
wp-navbar ==> xyz-navbar
Then copy the css code for wp-navbar from respective css file, replace occurrences of “wp-navbar” with “xyz-navbar”, and add it in “Internal CSS” option in HMWP Source Code tab.