Choosing a picture, a table or anything else

Put the cursor in the block that holds it, then press Esc. The editor selects it, just as clicking it would, and its own tools join the walk:

your text  →  text tools  →  picture tools  →  element tools  →  column  →  row

So to change a picture: cursor in the paragraph that holds it, Esc twice, and you are on Change Image, with Link, Select and Edit next to it.

To get from there to the text in another column, Tab leaves the tools for the content, or Esc walks all the way back to where the cursor was and Tab moves on from there.