to use a large font in the playlist (only), i change "zoom=0" to "zoom=7" in C:\Users\{user}\AppData\Roaming\vlc\vlc-qt-interface.ini
BUT this has to be done prior to *every* execution of VLC, as it's reset to 0 on exit

this is not an issue for me, as i use a batch file (PlayMedia.bat) to play media files - e.g.:
REM USE BIG FONT IN PLAYLIST (VLC RESETS IT TO 0 ON EXIT):
c:\mark\replace.exe C:\Users\mark\AppData\Roaming\vlc\vlc-qt-interface.ini "zoom=0" "zoom=7"
"C:\Program Files\VideoLAN\VLC\vlc.exe" %1
Note: replace.exe is *my* pgm. There are windows utilities available that will replace text in a file.
Linux:
vlc-qt-interface.conf contains "zoom=0", but changing it appears to have NO effect
if anyone out there can improve/correct/add to this info, please share!
VLC developers:
This really should be an option - esp as many of us use VLC with our home entertainment systems
(in which case the TV is some distance from the couch - making the playlist unreadable)