I can no longer see or search missing tracks. The left column only says Disc 1 of current album. How can I regain access to the search/ add function?
The way you do it now is to search for the missing tracks outside of the Fix Track Grouping feature (I just noticed that the description is a little misleading).
For example, in Album View you may have duplicate albums with some tracks in one album and the rest of the tracks in the other. You now right click (or long press) each album to highlight them, then click Edit at the top right of the screen. Then select Merge Albums.
Hope that helps.