What are these things on the A350's instrument panel?
These are the EFIS CP (EFIS Control Panels) for the captain's and First Officer ND's (respectively). For example, clicking on the ARPT button will display airports on the relevant ND (Navigation Display, the right part of the left screen, or the left part of the right screen in the image you provided).

It's pretty clear in this close-up photo.

You can see the mentioned controls in the top left corner and the ND display in the PLAN mode (which shows the entire flight plan).

The barometric pressure setting can also be changed using the EFIS CP.

Opposing your comment regarding the A320, The EFIS CP in the A32X (A318-A321)  is also in a very similar location.