I think I detect in the OP's question a suspicion, based on the airport floorplans, that upon entering the shopping mall on Level Four, one must pass through the security screening points in Concourse D. As I will attempt to clarify, that is not the way it is.

After passing through one of the three main passport-control areas from the Departures Hall to the Level Four shopping mall (i.e., leaving aside the fast-track entrance described by soju, there is no security checkpoint for access to any portion of the concourse areas of Level Four. The airport is laid out like this: +-+, with the concourses lettered A-B-C-D-E-F-G from the bottom of the left-hand plus sign to the bottom of the right, which makes the D concourse the hyphen in the middle. Level Four of the hyphen, the shopping area with the big golden sculpture, is also in the hyphen but one floor ABOVE the D concourse gates. All of the gates/depatures area, in fact, are on Level Three, below the shopping mall. When you're on Level Four, you can walk to any and all of the concourses on Level Four without passing through security. You pass through security at the ends of the Level Four floor areas (i.e., the floor literally stops, replaced by air at that height for the rest of the concourse building) for A/B/C and E/F/G concourses, whereas for concourse D, the security points are on the sides of the hyphen in the middle of the shopping mall. After passing through each security checkpoint, you immediately descend to Level Three. On the A/B/C and E/F/G concourses, you have no choice because there is no more of Level Four. Going onto the D concourse, you've simply gone down to the level below the shopping mall. Because of this, when you enter the shopping mall and want to go to concourse B and look at the planes, or concourse F or wherever, or just walk around to your heart's content, you simply bypass the security checkpoints for Concourse D without getting screened, because you're staying on Level Four, not going down to the secure area of Concourse D on Level Three.

The lounges for almost all (all?) airlines are all also located on Level Three, mostly arranged around the centerpoints of the plus signs. You access the lounges best by going down the escalators/elevators at the centerpoints of the plus signs. As soju and others described, when you leave the lounge on Level Three and want to go to your gate, you can either go back up to Level Four and get screened on that level only to take the escalator back down to level three for the walk to the gates, or you can stay on Level Three and get screened at a supplemental security checkpoint intended for lounge-users that is located just below the main checkpoint on Level Four. Once you pass through the checkpoint on Level Three, you'll already be on the depatures walkway and be joined by other departing pax as they come down the escalators from the main checkpoints on Level Four. The checkpoints on Level Three are typically less crowded than the main ones on Level Four-- at least for now, as few pax who aren't in the lounges even know about the checkpoints on Level Three.