Please see the video. I have enable Android 10's gesture control as someone said that was the issue. My phone is US version. https://youtu.be/b8e5JwS2mwo I first encountered this issue with Version WW-17.1810.1910.63. I have flashed .68's OTA and it doesn't help. I can't really wipe my phone as my phone has 1 irreplacable authenticator.
Even i got stuck two days ago but, I quickly found pretty easy solution for it. All you need is a Mouse ( wireless or wired ) and a OTG cable. Follow the video down below and everything will be back to normal. I will highly recommend to Turn off double tap home key gesture to enable One Hand Mode in Advance settings until this bug is fully fixed.
Thank god we have clever users that can think outside of the box 🙂 I tried gesture mode on a phone which I had never used one handed mode on before and it went through the tutorial without any issues. Don't know why this happened to you but good thing it all worked out in the end. Thanks @shiv1g