These references haven't been visible for years. Related to: - https://github.com/gohugoio/gohugoioTheme/issues/24 - https://github.com/gohugoio/gohugoioTheme/pull/216
.IsMenuCurrent is a method in Page object returning a boolean value. It returns true if the PAGE is the same object as the .Page in MENUENTRY in a given MENU.
.IsMenuCurrent
Page
true
.Page
You can find its example use in menu templates.