@pitaj that's it! Oh gosh, I literally couldn't see the connection of that ID. But now it all makes sense. Thank you!

@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: https://github.com/pitaj/nodebb-plugin-calendar/blob/2b9893dad12ee59bce494fe0fb24342f66cf9e67/public/calendar.less#L1 Then you just need to make sure your less is defined in plugin.json: https://github.com/pitaj/nodebb-plugin-calendar/blob/2b9893dad12ee59bce494fe0fb24342f66cf9e67/plugin.json#L31 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

Yes! That's it, didn't realised grunt was setup in a way to pick-up custom themes. It's working like a charm! Thanks a lot @PitaJ !