How to proper configure shortcuts for the menu completion when type [[]] ?

[barcell1]

i would like to set
: to go down
: to go up
: to select

but couldnt figure out how , also i tried in blink config

keymap = {
[""] = { "select_next", "fallback" },
[""] = { "select_prev", "fallback" },
[""] = { "accept", "fallback" },
},

but with no success

When i type (enter) it jumps a line instead of selecting