Macs support monitor Daisy-Chain / DisplayPort daisy-chaining / Multi-Stream Transport (MST) only by using USB-C Thunderbolt 3 cables.
Thunderbolt 3 - USB-C>USB-C cable that reaches speeds of 40Gbps
Dell Thunderbolt Docks and Apple USB-C Hosts
WD19S - UMSN's standard docking station. Does not allow for two external displays with a MacBook through this docking station.
You would instead need to use this dock in conjunction with a direct HDMI cable to the laptop
