As always sorry if this is already in the app somewhere... still learning the tricks after all these years.
In my workflow I usually want my columns sorted by album, but within the album I want things sorted by disc number and then track number. I can do this by clicking the Track, Disc, and Album headers, in that order. But if I need to change the sort for any reason, it takes a lot of clicking to get back. And it's always possible to make a mistake and open some new files without returning to my default... then if you do auto-numbering you could screw up.
So, what I propose is a preferences area where we can set a default sort order, specifying which columns to use... plus a checkbox for "apply default sort when opening files," plus a taskbar button for "apply default sort order."
I could see this being expanded to storing more than one sort order, with a few extra taskbar buttons so you can quickly switch around. But honestly in my case, the only sorts I use are the 3-level sort I mentioned plus a few single-column sorts ... saving multiples wouldn't help me out but maybe other people juggle multiple complex sorts.