This is exactly what I wanted, Porcus.
However, this zero width space displays as a box on my system in most fonts, including on the Wikipedia page. It works with Lucida Sans Unicode, and Adobe fonts, which I don't want to use.
I have come up with a solution using Thin Space and Hair Space characters next to it, which are 1 pixel wide. And to my surprise, there already is a crc32() function in Foobar.
$replace($select($add($mod($crc32([%releaseflags%][%releasedate%][%releasetype%][%label%][%catalognumber%][%media%][%__codec%]),16),1),0000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110,1111),0,$char(8201),1,$char(8202))
ESplaylist is good. I like the artwork display, and the grouping works as you say. But I cannot replace the normal playlist with it. I currently have about 20 customized columns for the default interface, which I display and hide as needed. There appears to be no way of saving them in ESplaylist. Once I "delete" a column by right-clicking on it, it is gone.