The premoves are still in development, so what I tell you here is the way it currently works.
The radial menu allows you choose for what purpose you want to premove the card.
The top selection means you want to play it.
The right selection (highlighted in your picture) means you want to discard it.
The bottom selection means you want to buy it.
The left selection means you want to react with it (it's a Reaction card like Moat or Clerk).
You can see it printed in the log, once you chose a selection.
If the next click you would normally have to do is for the specified kind of effect, the game uses your premoved choice.
