Today I upgraded my Teradata Studio 15.x version to the 16.2 version. In the Query Development perspective my Project Explorer seems to be pointing to a VERY OLD version of my projects. I see the path to my projects has changed. I changed the "Derby Database Location" to my active project area and it made no difference. How can I change the default location for projects to the desired folder so that the projects pick up all my current work without having to reconstruct each project one by one?
The project folders are part of your "workspace". The Derby database is just the SQL History, though it is by default also located within the workspace.
Edit the properties of the shortcut you use to launch Studio to append (or change) the -data "C:\path\to\desired\workspace\folder" option.
The default workspace location is normally %HOMEDRIVE%%HOMEPATH%\workspace-studio, e.g. C:\Users\yourUserName\workspace-studio (you can verify the actual path being used under Preferences / General / Workspace). If you didn't know the other workspace path, you could likely find it by searching for files named teradata.log; they should be in a folder named .metadata that is directly under the workspace folder.