Nodding while you text is a costume of listening. Everybody at the table can spot the zipper.

Attention is extremely visible, which is why divided attention never passes as the real thing. The nods land a half second late, the follow-up question repeats something already said, and the other person registers all of it without necessarily saying so. What they learn is not that you were busy, but where they rank.

Choose, rather than trying to do both. Either say you need two minutes to finish something, which is an honest and completely acceptable thing to say, or put the thing down. People forgive being made to wait far more easily than being half heard.