They should have a designated queue area, but still maintain those sitting at the bar. Alternate, one order for the seated, one for the queue. If you want to get fancy, replace the queue area with a cubby system and an app. Order from the app, pay, and get a QR code and a cubby number when your drink is ready. QR unlocked your drink cubby. The cubbies can be see through. I should invent this.

Numbered ticket dispenser is another option allowing crowding the bar yet orderly sequencing.