I manage my repertory with Microsoft Access (database with title, rhythm, tempo, sounds, styles, reg number and many others.
I use the song name (abbreviated) on the keyboard for registration name.
When I want to play a song, I search for its name (PC or listing), get the corresponding registration number and load this number on the keyboard (Ketron reg numbering). Anyone can use the list and ask me a number (kind of surprise). Over time, some numbers remain in (musical )memory.