Hey, @Rutger .
Tira here, from Shopify. Thanks for reaching out.
This is something that some merchants have requested. The URL for the order details page cannot be customized. I understand this may not be ideal and so I would like to forward this as a suggestion to our developer team so that they are aware of how we can improve our platform for you and all of our merchants. If we go ahead with this suggestion we will post an update in our changelog or announcements page.
What is your myshopify.com URL? I’d like to add your name to our feedback list.
I look forward to hearing from you.