Use the radio buttons in this multichannel block to select among sets of 4 inputs and send one set to one of the (4-channel) outputs.
To begin, drag the block into the workspace, right-click it and select Add Algorithm > IC # > 4 Channel/Slew or 4 Channel. (The result appears the same either way.) The 4 Channel/Slew algorithm lets you rapidly ramp the source level up and down without any clicking noises when switching among outputs. It uses N hardware volume controls in the target/slew RAM to do the job.
The default block (above right) is ready to use as a 2×1 connection, and like the others can be grown by right-clicking to select your desired number of input sets. The example to the right shows the default block grown by 3 (= 5 input sets total).