To search and/or filter the list, simply type what you want to see into the empty box above any particular column and push enter on the keyboard.
Example #1: to search for a particular horse, type all or part of a horse name above the HORSE column and hit enter on the keyboard.
Example #2: to search for all of a trainer's horses at a certain track, type the track abbreviation above the LAST TRACK column and then all or part of a trainer name above the LAST TRAINER column and hit enter on the keyboard.