The Manual Load Balancing is one of the modes available for Link Aggregation. As the name suggests, for this type of aggregation you have to manually create the Eth Trunk interface on the switch and then add member interfaces to it. In this mode, all membering interfaces will participate in the transmission of data flow. This is useful in a scenario where a high link bandwidth between two directly connected devices is required but the peer devices do not support the LACP protocol. The disadvantage of this mode is that this mode can detect link disconnections, but it cannot detect other faults like link layer faults or incorrect link connections.
You can find below an example of the Manual Load Balancing mode for Eth-Trunk:
