If you use a 3 switch box with a TRS (tip ring sleeve) connector you can assign one of those swiches to tap. In fact, the default mode for the external switch, when the unit is in bank mode, should mirror the play mode functions.
I bought one from 'red onion solutions' in the UK. Small size like an old MXR pedal so doesn't take up too much room on your board. Highly recommended. You want the 'triple momentary' in the 'general purpose' section.
Thank You!…I've read here about the Boss fs 5u which is a single switch box, I guess is not good for my purpouse (to be able to tap tempo in the bank mode)…can you suggest me a 3 switch box?