After adding annotations to messages, according to the manual, "a new faceted browse section, Annotations, will apear in the results on the Search Results screen."
I have not been able to make this happen after clicking the annotations box, entering my annotation, and clicking "apply." Further, if I navigate out of that particular search and try the search again, the same message does not appear to have the annotation attached to it, nor do the annotations appear in the Review for Export tab.
The behavior described above occurs when working with an MBOX file converted from a PST using libpst/readpst.
The command used to create the MBOX was:
readpst -r /path/to/PST/file -o /path/to/outdir
-The result was a set of MBOX files--one MBOX for each folder in email account. The total size is comparable to that of the PST file.
When working with an email MBOX file exported directly from Google (also, different account), the annotations feature works as described in the user manual.