Is there a way to get a new registry recognized without rebooting?

That all depends on the application that is using the registry key. When a key is updated, it is updated, but an application may only look at the key at startup. Rebooting is just a simple way of ensuring that the new key is loaded.

"The best way to get the registry refreshed is to kill the Explorer.exe process via Task Manager. That way, the registry is reloaded (on old trick that has worked since Windows 95).

Although I am not sure if the entire registry or only part of it is reloaded, @Gnoupi 's advice to logout and log back in helps as well."