Well, you could use a serial port on each device with a very simple protocol.
The various nodes are connected so that:
UNO (Master) Tx -> NodeMCU #1 Rx
NodeMCU #1 Tx -> NodeMCU #2 Rx
NodeMCU #2 Tx -> NodeMCU #3 Rx
NodeMCU #3 Tx -> NodeMCU #4 Rx
NodeMCU #4 Tx -> UNO Rx
The UNO sends out a simple query packet such as [2] (left square bracket is the start marker, 2 is the data /address and right square bracket is the end marker).
NodeMCU #1 receives this packet and knows it is not addressed to it, so simply retransmits the packet.
NodeMCU #2 receives the packet and knows it is addressed to it, so responds with its readings. The data packet might be: [0,reading1,reading2,reading3].
NodeMCU #3 receives this packet and knows it is not addressed to it, so simply retransmits it.
The packet gets passed along until it eventually arrives back at the UNO.
The Serial Input Basics tutorial will get you the basics of packet reception - see example #3.