Hello Kim Asplund,

You do not need to add code to the HTML/CSS editor. Just change the configuration on the website header

Here, I share the configuration for the moving language selector to the header.

Step-1: Open the website editor mode and click on the edit button top right corner.
Then select the header part of the website and you see the “Language Selector” button.
Also you can see the below image.

Step-2: Then, open the “Language Selector” button you see the three options None, Dropdown, and Inline.
As per your requirement select the option “Dropdown” in the “Language Selector” button and click on the Save button.
 

Step-3: After saving the configuration you see the language selector on the header.


I hope this solution is helpful for you.

Thanks & Regards,
Email: odoo@aktivsoftware.com
Skype: kalpeshmaheshwari