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In addition to just the nice, terse syntax, you can do things that HTML can't, like loops.
To activate Slim, choose it from the HTML Settings:
Emmet doesn't output in Slim (yet), but you can write regular HTML right within Slim (like Markdown or Jade can as well), so we left it active. We did update our custom tab triggers to output in Slim though, for instance try ul-TAB: