You can flip a window in/out of maximized mode by double clicking on the title bar. That works for the Save-As window too. Windows itself remembers the Save and Save-As window position and size for each application. Unfortunately, while it’s in the registry the data is buried in a blob within HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\CIDSizeMRU meaning it’s not easy to go in and reset an app to the defaults.
If you ever are jammed and can’t see or get to the top of a window then do Alt-spacebar. You should get the same menu that you get when you use the mouse to click on the upper-left corner of an application. This trick works even if the window is dragged 100% off the screen and is not visible. You will then have either “Restore” available if the window is currently maximized or “Size, Move, and Maximize” options Using this menu you can also move and resize a window using the arrow keys to drag it back on screen if needed.