Hi there! Sorry if it is obvious but it is possible to define meta tags (such as the lang one) directly in Plasmic Studio? (and attribute to the html tag) (i use the headless api with next) Have a great day! 
Hi! Typically these are defined in the code base outside of plasmic since many of them tend to be site wide or associated with a specific subfolder or subdomain based on the internationalization configuration
Thank you for your answer! It is just that I struggle to understand where to define the “html structure”. I mean it looks like that the PlasmicLoaderPage already inject the html tags as well as the head tag.
Alright my bad it is not related at all with Plasmic but with Next.js.
Here’s a few resources for noobies like me: https://nextjs.org/docs/api-reference/next/head https://nextjs.org/docs/advanced-features/custom-document
Thank you and have a great day!