The Huawei Mate 10 Pro can use DisplayPort Alternate Mode through its USB Type-C connector which means the phone should be able to access most external displays supporting DisplayPort including the ASUS MB169C+ USB Type-C Portable Monitor. Rather as seen here the phone wouldn't seem to connect properly with the Asus display using the USB 3.1 Type-C to Type-C cable that came with the monitor.
Once attaching the Huawei Mate 10 Pro to the ASUS MB169C+ USB Type-C Portable Monitor, the phone initially showed some quick tips for using screen projection mode. When initiated the phone was never able to connect or establish screen mirroring with the monitor. Unfortunately the Huawei Mate 10 Pro can't work over DisplayPort with certain USB Type-C displays like the ASUS MB169C+ USB Type-C Portable Monitor.