Place duplicated tracks underneath the original/source track by default.

When a track is duplicated, the new track should appear below its original/source track by default.
Perhaps this could also be configurable in the Preferences section, such that a user could decide if they want duplicated tracks to appear underneath the original track or at the bottom of all existing tracks (as is the current functionality)

This will probably be implemented at some time in the future.

Since very early in Audacity’s history, newly created tracks were always added below the last track in the project. We are gradually migrating to a different behaviour which is to add new created tracks below the selected tracks.

See this proposal in the Audacity Wiki: