No, it is not possible to display flow direction arrows using the ArcGIS Utility Network in ArcGIS Pro. This functionality may be available in the first quarter of 2021.
A trace network can be used to display the flow direction arrows. To do so, perform the following steps.
Note: Junction points are needed to display flow direction in a trace network. For example, in a gas flow network, these junctions include features such as valves. These junctions are essential for generating the flow information in a network. The network topology cannot be constructed for the data models without the source and sink details supplied by junction data.