SugarSS is a PostCSS parser for indented syntax and neither the PostCSS grammar used in Vetur or the extension below support the indented SugarSS syntax with the source.css.postcss language source
Adding lang='sss' and lang='sugarss' that sets the region's language to source.css.sugarss will add highlighting when postcss-sugarss-language is installed, like with SASS support. This'll also support Stylelint.

I'm not against adding SugarSS per-se, but the extension you are pointing seems to be the only one having SugarSS highlight, but I don't like that extension since it claims to be supporting PostCSS when what it really does is using the SCSS support from vscode-css-languageservice...
I could find a SugarSS syntax myself and add it to Vetur. But now I've become a bit hesitant about adding just syntax-highlight support for new languages, since people would start to ask for other language features for them, which I don't have time for.
If possible I'm trying to spend more time to deepen the support matrix for languages, like adding richer support for pug/stylus/sass, instead of trying to widen the matrix.
@octref Since stylus is nearly abandoned (https://github.com/stylus/stylus/issues/2282), many people (including myself) are looking for an alternative and sugarss seems the one, that's why could be as important, is not like "widen the matrix" is more like a replacement.
It would definitely be nice to have this issue resolved if possible.
A lot of projects at my work are using SugarSS so it would be great to get syntax highlight support.
Would it be okay if I tried to make a PR for this?
It would definitely be nice to have this issue resolved if possible.
A lot of projects at my work are using SugarSS so it would be great to get syntax highlight support.Would it be okay if I tried to make a PR for this?
The PR is welcome without https://github.com/vuejs/vetur/issues/662#issuecomment-360242512.
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It would definitely be nice to have this issue resolved if possible.
A lot of projects at my work are using SugarSS so it would be great to get syntax highlight support.
Would it be okay if I tried to make a PR for this?