In 6.4 studio I found a small bug.
The lookuppickerfield component supports action edit and you can add buttons to the component (BIG APPROVE).
When you add ‘open’ action then the screen designer shows ‘…’ ellipsis, but in the running app there will ‘looking glass’ and will fire the lookup or edit action.
When in screen designer we add action ‘lookup’ the designer shows ‘looking glass’ icon, but the app will show ‘…’ and firing the open action.
So the lookup and open actions are reversed in screen designer and in the running app.