Matt, the PhotoGeek, shows how to accelerate access to Lightroom Plugin Extras:

If your directory does contain a TranslatedStrings.txt file:
1. Open TranslatedStrings.txt in a text file editor
2. Search for the string “AgSdkMenus/Menu/PluginExtras”
3. If the string does exist, add an ampersand (&) into the text following the equals (=) sign. This should be placed immediately before the character you want to be the accelerator. e.g.
“$$$/AgSdkMenus/Menu/PluginExtras=Plug-in Extras” would become “$$$/AgSdkMenus/Menu/PluginExtras=Plug-in Extra&s” to make s the accelerator character

I'd also wondered why Adobe didn't give Plug-in Extras their own an accelerator key, so from now all my plug-ins will be written with this tip in mind. In the medium term though, surely we'll be able to add menus exactly where we think is appropriate.

Here is my own TranslatedStrings.txt file. I've used “u” as the shortcut because Matt's choice of “s” works for File>Plug-in Extras but not for the Library>Plug-in Extras menu (because it's already assigned to Synchronize). My file also corrects the Ansel-Adams-corpse-spinning use of “grayscale”. Apologies for the language, “g***scale”, I mean.