Shopify - Native menu
In this article, you will see how to create a native menu on your website
Go to Shopify Admin > Apps > Weglot Translate > Online Store > Navigation section and select the menu where you want to add your button.
Then, click on " Add menu item" and add languages you choose in Weglot.
Click on "Edit" and add the related link. For instance, for the English button add #Weglot-en, for a French button you will have to add #Weglot-fr, here is an example below: