There are several reasons why you might want to delete saved wireless networks from your Xiaomi smartphone, one of the most common being reconnecting to your home network because somehow a mistake has crept in and the Internet is slower than usual.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Wi-Fi
Step 3:  Tap on  Additional settings
Step 4:  Tap on  Manage saved networks
Step 5:  Choose a saved  network
Step 6:  Tap on  Forget network
  1. Open the Settings
  2. Tap on Wi-Fi
  3. Tap on Additional settings
  4. Tap on Manage saved networks
  5. Choose a saved network
  6. Tap on Forget network

Xiaomi Instructions