For sound normalizing you can use a normalizer in Cinegy Air.

To send audio from the Sequence to external software and back to the Sequence after correcting it, you can export only the audio track to WAV from the sequence, edit, re-ingest, and add it to the sequence as an additional audio track.

Then delete the original sound.

For the third-party solutions please refer to: https://www.telosalliance.com/file-based-audio-processing/audio-automation-for-enterprise/minnetonka-audiotools-server or https://www.magix.com/ca/music-editing/sound-forge/