join joins all children into an array-like structure along a given dimension. The first child remains fixed in its original position. the rest of the children are arranged to form a line on the min or max side of this first child, and they are centered along the other two dimensions

Let's consider a simple case involving a large cube and a bunch of small cubes. Initially, they are overlapping; we can only see the large cube because of this. After adding l="join x" to <g>, all small cubes are moved to join the large cube to form a line along the x axis; and all are centered with respect to the large cube.

join can optionally take a number, such as join x 3 to specify how much space to put between every two objects.

A side min or max can be specified to indicate which side of the first child to join the rest of the children to.