How to power-on without using POWER button, Xiaomi/Redmi Phone
When phone is Power OFF:
Press and Hold VOL-UP button, Insert USB Power cable, to enter Recovery Mode.
With Reboot option selected, just WAIT, the phone will reboot in around 4 minutes.
Tested on Xiaomi Mi 10 Lite 5G, also Redmi 5 Plus/Note 4X.