You can customize the Shortlink to whatever name you want as long as that name is available.
The method is as follows :
1. Login to S.id and go to the Dashboard
2. Select the "Link" menu
3. Select the shortlink you want to change and click Edit
4. Change the name to your liking (as long as it's available) then click save, and also a title
5. Congratulations, your link has been successfully changed