No (Picard is the MusicBrainz tagger after all), but there are tools that help you importing releases from Discogs into MusicBrainz. See e.g. this discussion: Is it possible to import a recording from Discogs? - #2 by IvanDobsky
Just curious: Do you have some examples of the releases you could not find in MusicBrainz but on Discogs?
You can drag and drop files from one track to another.