1) org.eclipse.jdt.USER_LIBRARY setting can be found at
D:/workspace/.metadata/.plugins/org.eclipse.core.runtime/.settings/org.eclipse.jdt.core.prefs
OR
2) You can also export the old workspace's USER_LIBRARY to a file first, such as userlib.userlibraries, and then import it in the new workspace.
D:/workspace/.metadata/.plugins/org.eclipse.core.runtime/.settings/org.eclipse.jdt.core.prefs
OR
2) You can also export the old workspace's USER_LIBRARY to a file first, such as userlib.userlibraries, and then import it in the new workspace.