Windows 10 BCDEdit - How to change {bootmgr} path?

In Windows 10 you have to quote {bootmgr}. The new line is

bcdedit /set '{bootmgr}' path \EFI\refind\refind_x64.efi

If you're using PowerShell you need to quote as answered by @zauguin.

Another option would be to use CMD, which is the terminal that the rEFInd author used when writing the guide.