I’ve just verified on the devkit for changing boot order.
I think you might not use “-” to change boot order.
The overall steps to change boot order in UEFI is as following:
Step 1: Enter Boot Menu
When you see the NVIDIA logo at boot up, Press "ESC" to enter setup.
Step 2: Change Boot Order
Boot Maintenance Manager -> Boot Options -> Change Boot Order -> Press "Enter" and a prompt showed up -> Press "-" to Move Selection Down -> Press "Enter" and the prompt vanish
Step 3: Save and Exit
Press "F10" to Save -> Press "Y" to Confirm -> Press "ESC" 3 times back to Boot Menu -> Select "Reset" and Press "Enter"
If you still have problem about changing boot order, please provide the serial console log and also the screenshot of boot order menu for further check.