Trionic Labs

SASS is a programmable approach to stylesheets which really adds some cool features. It can make a stylesheet easier to read, easier to update and also adds some powerful features like functions, variables and imports. (See http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html for more details.)
This plugin enables any WordPress Theme to use SASS stylesheets. In a wordpress theme, the comments at the top of style.css are used to define the theme. For this reason, this plugin will not allow a .sass or .scss file named ‘style’.

WordPress SASS

This plugin provides automated SASS stylesheet generation.

wpbits

Custom CSS for Blocks allows you to easily write custom CSS for any block or post on your WordPress website, giving you complete control over the design of your content. You can take advantage of SASS support to write clean, efficient code. And, with optimized inline output on demand, you can ensure that your website loads quickly and efficiently for your visitors.

WordPress SASS vs Custom CSS for Blocks