In Filemaker 8.5, I had a custom Record menu with a "Go To" submenu with items First, Previous, Next and Last. This still works in FMP 11, but at the cost of disabling the navigation items on the status toolbar. That is, if you want the navigation items enabled, you must have FileMaker's own "Go to Record" submenu installed somewhere in your menus. Or am I missing something?

I believe you are correct.

The rationale is that if you disable the Go to Record menu item then you don't want the user to be able to navigate around by themselves, so the status toolbar nav buttons are also disabled.

The converse must also be true: if you allow the user to navigate with the buttons in the status toolbar, there should be no problem letting them do it with the menu commands (since it's doing exactly the same thing).