Hey there old friend, @JTPets 😆
Currently, the Square Register and Square Stand are designed to support one staff-facing screen, and one customer-facing display. Square’s system doesn’t officially support running a third display at the same time. For example, you can’t have two customer-facing screens connected to the same Register or Stand.
If you slide in the customer display to the device expansion port, that will become your dedicated customer display. Plugging in another external customer display at the same time won’t work. The Register won’t know how to output to two customer-facing screens at once, and it could cause unexpected behavior.
Workaround ideas:
If you have a second Register that’s unused, you could set it up as a second full POS instead. So you’d have two fully functional Registers, each with their own staff and customer displays.
If you want to show things like promotions or menu items on an extra screen, you could run a separate digital display or tablet that just mirrors certain content, but it wouldn’t directly show live transactions from the POS.
