I have a Lenovo Yoga 720 laptop with Windows 10 installed. I was attempting to install Ubuntu 18.04 as a dual boot option. I was able to install Ubuntu, but encountered some difficulties in that during the boot up process, I was not seeing an option to choose between the two OSs. I had to press F12 manually and select from one of the choices to boot into either Windows 10 or Ubuntu 18.04. I think this was because I had installed Ubuntu in legacy mode, but later found out that I should have installed it in UEFI mode instead.
To start over, I removed the Ubuntu partitions using the Disk Management application in Windows. Now when I boot, I either get an error and go into GRUB rescue (I tried Boot-Repair by loading Ubuntu using a live USB to no effect) or have to press F12 again, after which I go to the screen shown below. From there, I have to choose the second option to load Windows 10. How I can remove the first option from the Boot Manager, so that Windows loads automatically without choosing the 2nd option from the Boot Option Menu whenever I start my laptop?