Where to start and end kitchen backsplash?

Not what you're asking about, but important:

If you regularly plug in more than 2 devices, as implied by the 6-1 gadget in the picture, then I highly recommend putting in another dual 15A receptacle a few inches away from the existing one. It can be on the same circuit and on the load side of the existing GFCI. I would put it a few inches away (either above the existing receptacles or to the left, below the light switches - presumably there is a stud between the switches and the receptacles) rather than putting in a 2-gang box because many devices need extra room (e.g., wall warts). It can share the same circuit so the cost is basically standard dual 15A receptacle + box + a little bit of cable and appropriate clamps, etc. This solves two problems:

• For now and the future it eliminates the extra plug-in gadget to "expand" the receptacles. I use those, but I hate them. When there is a specific need - e.g., provide surge protection, then they make sense. But when they are just to add more receptacles they become another point of failure.

• Doing this now, before you tile, means you don't have to do extra work patching. If you do a half-way decent job, any mess (extra holes, scratches, etc.) will be totally covered up by the tile! Very convenient.