Hello GrinGEO,
Depth maps are intermediate product of the processing. They are the source data for the dense cloud and for the new meshing method.
If the depth maps are present in the project and you are selecting the further processing option that assumes depth maps generation, then you will be able to re-use them (skip there generation again), providing that the same quality/filtering settings are selected.
Note that new mesh currently requires only depth maps generated with Mild filtering option, so in your workflow you would be able to re-use depth on Step 6 (build mesh) only if on set 3 (build dense cloud) you have used Mild filtering option, and on Step 6 select the same quality as on the Step 3.