I'm also in search of a tweak to change the default location selected on "save as" dialog window
That's stored in the OpenSave MRU, on a per-app or file extension basis.
HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\OpenSavePIDlMRU
I'm assuming if you never saved any files, it defaults to some home folder. Unless you had a tool which constantly flushed the MRU or modded the most recent item, I don't see how you keep the same folder location.