Cool - was genuinely wondering if I'd missed something!
As goes visual nav, you have a requirement to have a positive fix of your position at not less than certain intervals, which in practice means you need to have regular sight of the ground even above 2000 - I believe the guidance is over no more than 4/8ths. If you're signed off to be able to navigate by specific aids (NDB/VOR/DME), you can fix that way, and need not see the ground. You generally do that with the night rating. Although it's perfectly reasonable to get that signed off for regular day VFR it's not normally part of it.
Obviously that doesn't mean you can't use them to supplement visual nav, but not soley.