I was wondering if anyone else has this problem.
After the 1809 update I've found that all the PCs I have applied it to so far have the same symptom of very slow access to the New submenu in Right Click Context menus. It seems when you first open the right click menu and scroll to the New submenu there will be a long delay before the submenu opens which freezes the Context menu. Once the New submenu opens you can roll the mouse cursor on and off the submenu and it will close and re-open quickly, but as soon as you allow the Context menu to close and try the re-open it the problem returns. It appears to be some problem with background enumeration of the menu.
I also notice on a couple of machines the New submenu now contains far fewer items after the 1809 update. Some of the systems have a lot of software installed so usually have a long list in the New submenu, others are basically vanilla content machines for browsing and just have the defaults with Office 365.
This happens over the desktop or in any open Explorer window.
The five machines I have upgraded are from a variety of manufacturers(Dell, Acer and Asus) using different processors(new and old), graphic cards(AMD, Nvidia and Intel), etc., etc., so it seems it is not associated with any specific hardware. I have had no other obvious problems with the 1809 update.