It is possible to discover the devices via Modbus TCP/IP if the network is built on IP devices. In order to start discovering, make sure that the PC is connected to the same network as the devices, and it has IP address in the same network segment.
The example of device connection is shown in the figure below.
In case of the Modbus TCP, the devices discovered recently appear in the list only with IP address and information that they are not identified. In order to make any changes to the devices, it is crucial to identify them. To do so, right click on the device in the tree and choose Identify and Discover Gateway Devices option.