Your file open/save dialog feel like it's from Windows 95.  No right-clicking in the window to View, Sort by, Group by, New (Folder, Shortcut, etc).  Address bar is not editable...in short, implement modern, Windows 7, Windows 10 file dialog. 

Also, what's with the default directory?  Personally, I do not save to SQL Developers crazy default directory "c:\users\<myname>\AppData\Roaming\SQL Developer\system18.4.0.375.1900\o.sqldeveloper\projects".  I mean, what is this for a default directory?  Very out of touch.