>> The following Audacity 3 features are not available in Audacity 4.0, but we're working on adding them in future releases.

Time Tracks Note/MIDI tracks Mixer Macro Manager and the scripting pipe VAMP and LADSPA plugin hosting Play-at-speed Sync-Lock and the old tool modes were replaced by the workflows described above.

>>Additionally, Audacity 4 ships with some missing exporting and rendering features, analyzers, and effects.