Hi Chris,
do you want to select the clips or trigger the clips?
Selecting clips with left/right/up/down is not available out of the box, if you want to trigger you could use '/composition/selectedlayer/connectprevclip' and '/composition/selectedlayer/connectnextclip' for left and right. For the layers you need to chose them explicitely, there is no next/previous layer OSC-command.
A similar question was already brought up here, if you want to read into it:
viewtopic.php?f=12&t=15550&start=10
Greetings,
Christoph