I would like to put in my vote for a configurable User Library path please.
I’m on a Mac. It bugs me when applications decide to put stuff in my Documents folder. I’d rather have the Renoise user library in my ~/Music folder. The symlink workaround is ok but I’m still left with that thing in my Documents folder.
If it’s purely about disk space, symlinks would work. If you want to keep your directory structure clean and you happen to be on Windows, you could just hide the directory (or the symlink, if you’re using one).
On Linux or Mac, you would have to use some kinda sandbox to prevent Renoise from creating the directory in the first place, and then just use the preset system as before.
This is definitely something that should be made configurable (even if it’s not exposed in the options dialog and hidden away in Config.xml).