Smart Search (the "walking man" icon present during playback) disappeared when I updated my NV4108-HS (Hardware Version V1.0) to V4.000.00AC000.0 firmware. Smart Search reappeared when I entered full screen mode during playback (icon in upper right of video pane) and activated the control tray by moving the pointer to the bottom of the screen.
I wonder what Amcrest intended for Smart Search. A manual dated Oct. 12, 2018 describes Smart Search. A manual dated Nov. 23, 2020 does not. The functionality is useful enough to me that I am glad to have it back.