Beginning of Chapter 4: I discovered this after finishing all of Chapter 5.
The only part that has anything to do with belly buttons at all is... A quote.
"Woah... Deep..."
...That's all there is about 'belly button exploration'. Just a quote from Niven: only walk over a belly button, rather than go in and get her greasy lint 🥺. There is no belly button exploration 😭.
You might be wondering why I mentioned 'lint' here? It's because of this:
"This journey (eventually) will contain a variety of nasty things, and is only for players that are 18+"
And there were so many places a belly button could've been accessed, spelunked, or dug out! 🥺
Like here (there could be many more; Just imagine Maeve's belly button for a cavity)
Enya's first interaction of her belly (prior to the belly button in Chapter 4)
Niven is just beside Maeve's belly.
Maeve's entire body (including belly button; sadly an untouched potential)