I really appreciate that Picard 2.7 has support for extracting features with AcousticBrainz.  The AcousticBrainz GUI is not nice to use, and being able to scan the files I'm working on directly in Picard is very nice.  There are some improvements I can think of.

Change number of extractor processes

When extracting features from multiple files, up to eight instances of streaming_extractor_music.exe will run at a time.  This is too much for my CPU, and my computer becomes almost unusable at 6 or more extractions running at once.

An option to limit the amount of extractions running at once would solve this.  See attached image.

Skip extractions for recordings with existing AcousticBrainz analysis

An option to skip extracting for files with linked recordings that already have AcousticBrainz data would help make the intense process more efficient.  This is helpful for large albums, and especially for compilation albums that may already have recordings with analysis done from other releases.

Show if a linked recording has an existing AcousticBrainz analysis

Related to the previous point, it'd be nice if the column for "AcousticBrainz status" could show if a linked recording has an existing analysis.  Right now, it only tells me if an analysis has locally been done in this session of Picard.

In the meantime, I can tell if there is existing analysis for the linked recording by selecting a track, and seeing if there's a field for "BPM" and "Key" in the tags editor.  This is possible because I use the plugin "AcousticBrainz Tonal-Rhythm" by Sophist, Sambhav Kothari.