There's a track selection issue with a sub-grouping setting.
If "precede with a blank line" is not ticked, you can't select only first group (say disc 1) tracks without including disc 2 tracks on the left column (via shift+click selection).
If the option is ticked, it works. But if there are any tracks ungrouped by the setting (say no disc# tag), then shift-selection still selects other groups' tracks. But maybe this is expected by the nature of the setting.