Going to:

https://app.short.io/add?domain=yourdomain.com&apiKey=blahblahblah&originalURL=https://google.com/&custom=google&tags=website,link&folder=urls&expiry=none/

for example, would add the link Google.com as your domain.com/Google with no expiry and website and link tags and be in the URLs folder. This would enable you to easily add it as a "search engine" where for example you can just type "short" into your address bar then space and paste a URL. (by putting %s instead of the URL)