Both itemDef examples are from eXtreme+ rcon_playerctrl.menu. The one I quoted is for displaying a player's name for a specific slot, and that's what the OP wanted. Nothing is missing at all.
Your itemDef example is for setting a player action in eXtreme in-game RCON. Although the dvar/dvarFloatList stuff is good-to-know for some readers, it's certainly not required.

btw: dvarFloatList and dvartest are totally unrelated. dvar and dvarFLoatList are related, and dvartest/showdvar/hidedvar are related.