Hi Vincent,
Thanks for your update.
As you mentioned, we have provided the online document to localize the strings of grid. You can avail the details from the below link,
Also, we provided a dashboard sample which will be available in your local machine from the below location,
Dashboard sample: <Insatall_Location>\Syncfusion\EssentialStudio\<Product_Version>\Windows\Grid.Grouping.Windows\Samples\Localization Samples\Localization Demo\CS
Please let us know, if you have any other queries.
Regards,
Arulpriya