Allow placing folder notes outside of the folder, e.g. by using a prefix `../`

(Not sure whether this is a feature request or a bug in an existing feature.)

I already have index notes that live *outside* the enclosing folder, i.e.

```
.
├── foo.md
├── foo
│   ├── bar.md
│ └── bar
├── baz.md
└── baz
```

I'd like the auto-generated part to be included in those notes. I can set note name prefixes without `/` and the custom name feature works fine, but if I set it to e.g. `../` then nothing happens (including no error messages / warnings in the console.)

This should either work or produce an error message of some kind. (In the latter case, I'd also love to see a feature that would allow this mode of use.)