Yes, you can dig up the plants, place them in the shade, remove the mound of soil and replant at ground level. But I do not see any advantage in doing all that work. Your plants will grow better on a raised mound and the years of bark have now composted creating excellent soil. If the bark is infringing on the sidewalk cut back the mound to widen the sidewalk and add more stones to raise the level of the retaining wall. Perhaps a groundcover such as hard geranium can be used in this bed as a living mulch instead of adding bark chips each year. Keep growing, Marianne Binetti