1. Join a draft event.
2. Click on a card and start to drag it. Keep holding it and let the timer run out.
3. In the next pack, you won't be able to select cards. If you click "pick now" it disconnects you from the draft. You have to restart the client entirely.

(As a bonus, when I restart the client and reconnect to the draft midway through, it seems like the arrows that show up when targeting a spell are broken. I can see the point of the arrow but not the line.)

This happens to me a lot toward the end of packs when the timers are short, and I often miss other picks while waiting for the client to reconnect. It's very hard to break the habit of dragging cards while I think about them, especially since that's also the easiest way to put something directly into your sideboard.