Here is the generated reg file:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\Software\Policies\Google\Chrome]
"ExtensionSettings"="{\"*\":{\"runtime_blocked_hosts\":[\"*://ycombinator.com\",\"*://boh.com\"]}}"
Tested in a new Windows 10 x64 (2004) VM with a new install of Google Chrome 81.