WSOD when trying to configure menu with many items
A fiddly workaround:

On the "list links" menu page, you can visit, rearrange, enable/disable, edit, and delete all menu items. Except for visiting the node, all this is possible from a single menu item’s edit page. 

But how to access the menu item edit page without being able to access the parent’s menu page listing all those items?


Visit the node whose corresponding menu item you want to edit.
Open its HTML source code.
Search (Ctrl+f) for active menu-mlid. You’ll find a class value like menu-mlid-218. 218 is the menu item ID.
Visit /admin/structure/menu/item/218/edit.