No, you cannot daisy chain "just" data between two monitors. The U2723QE #8 USB-C upstream port is only used to connect to the computer. The U2723QE #15 USB-C downstream port only provides data to and from the computer. Because the U4919DW is NOT daisy chained from the U2723QE DP out port, there is zero data communication between them. To get operating system access to the U4919DW five USB-A ports, you must connect the provided USB-B to USB-A cable from the U4919DW #6-1 or #6-2 USB upstream port to a USB-A port on the Precision 7520.
Daisy Chain of Dell Monitors. I have a Dell U2723QE and a Dell U4919DW that I run together, mostly for video editing. The U2723QE is connected to the computer via HDMI (Picture and Audio) and a USB-C cable (Data).  The U4919DW is connected to the computer via the Display Port.  These are each driven by one of the two GPU's within this computer. This allows great performance for video edit, where by the main edit software is run on the wide screen and the playback, especially if using multi camera is on the U2723QE. In order to be able to use the USB ports on the U4919DW I have added a High Performance USB Cable between the two monitors this cable was sold as having a capability of 100W and 40Gbps.  However, I am unable to see any hard drives connected to the U4919DW.  I am only interested in this possibility - data transfer.  There is no need to have a second stream of video, or a power supply, unless that is required to drive the HDD, but I believe that this comes from the screen.  For the sake of good order, these ports function when the USB-C outlet on the computer is connected directly to the U4919DW. It is noted that the USB-C out port on the U2723QE is an "upstream port".  Is the problem, no "downstream" traffic? Is there anyway that the "hub" on the U4919DW can be used like this.  I know already from the forum it is not possible to daisy chain the U4919DW in the opposite sense, - that is as the "first" in the daisy chain. The driving computer is a Dell Precision 7520.
U2723QE, U4919DW, daisy chain only data?