Let me preface my message by stating that i don't agree with how OS-es coddle people and not allow them to do whatever the absolute hell they want to their own (file)system. And i don't agree with the unsafe argument (at least partially), because last i checked, tons of applications can access and write to directories all around the filesystem; Composing software, Drawing programs, not to mention 3rd party file managers.
File dialog windows, ones given to you by the system that is, are hard to access and get to work (and they are OS-specific too, so you'd need to code it more than once per platform through the FFI, if you even could); Accessing any other part of the filesystem though was always possible, through lua's own io system. (At least back in the day of 0.7.x onwards, that's when i joined, so i can't say if it was possible before, but it probably was)
That said, i'm working on a lib (with the FFI as well) to allow you to access any place on your filesystem through love.filesystem as well (granted it may be limited in usage if your OS would block your app from accessing certain directories), and with that, one could write a graphical element akin to a file dialog window, so that they could access any files anywhere.
Downside is that if you compile löve against anything but luaJIT, my lib won't work.
Writing files would be harder to implement though, by way of PhysFS (that löve uses) can only ever have one simultaneous write-directory, and if you wanted to write to more locations, or keep files opened for writing, it would fail to dynamically change said write-directory. I'm still thinking about whether i should just code around that, or use lua's io functions for saving/writing data.
Finally, since löve is more or less an educational tool in my mind, helping people make games being the most common denominator, i still believe it's fair that its own filesystem implementation has such limits; at least you can know that by default, these projects won't litter your filesystem with files, but it still gives you ways to go around said limits. 