Was scanning through some random "macro guides" and have yet to come across it, and it was bugging me having to manually add it...So, in case nobody has figured it out yet (or are having too much fun playing to come tell people), the way to equip "Veteran Trade" (and possibly all traits, as well as other gathering & synthesis abilities...needs testing.) via macro, is this:
/equipaction 1 "Veteran Trade"
Since it's not considered a "Battle Action", it get's automatically slotted in it's appropriate section, so no need to worry about it removing what's in your battle action slots, that are of the same number.
Hopefully, we're just missing commands, as we're still in beta, and come launch we'll be given the full command set, with appropriate modifiers, to prevent confusion for new and old players alike that may not read random posts like these.