@paladin884 what do you mean that won't work? What did you try?
Here's me importing a CSS fine directly into less in one of my plugins:
Then you just need to make sure your less is defined in plugin.json:
You can instead just add it to your plugin.json under css like so:
{ ... "css": [ "path/to/stylesheet.css" ] }Either of those options will result in it being added to the main css file loaded in header.tpl
