good one Brian
here's what i've been using since before the ~expand modifier
make a new smartlist
right click the new list, edit>import export
paste the following into the box
[=save(0,var_disc_sum[album artist (auto)][album])1]=1 [=save(math([disc #]+load(var_disc_sum[album artist (auto)][album])),var_totaldiscsum[album artist (auto)][album])1]=1 [Media Type]=[Audio]
now, in the smartlist right click on the columns>add expression column
paste the following into the box
load(var_totaldiscsum[album artist (auto)][album])
now you can sort by that column...point is, if the number is 0, the disc # field is empty. if the number is 1, you need to fix it. if the number is greater than 1, it's part of a multi disc set and you don't wanna erase the disc 1 value by accident...so only change the ones equal to 1
also you can paste into the expression column
if(isequal(load(var_totaldiscsum[album artist (auto)][album]),1),FIX,.)
which allows you to sort by either FIX, or the field is empty
this will only work of course if your album artist (auto) is tagged. if not you can change things a bit...