Direct call

Have you tried the following steps:

1. Open Contacts.
2. Tap a contact.
3. Tap the three-vertical-dot Menu button.
4. Select 'Place on Home screen.'
5. Then pick Dial dial. (see attached screenshot)

If you don't the direct dial option, your new xiaomi phone must be using the Google dialer, then you might need to explore third part apps such as "Speed Dial Widget - Quick and easy to call" to have the contact widget added on your home screen.