In some cases, it is required to plot a set of columns in the x-axis against one (or more) columns in the y-axis. For instance, in type curve analysis you may want to plot gas EUR or oil EUR on the y-axis versus lateral length, total proppant, proppant intensity, proppant per entry point, etc. on the x-axis. It is currently possible to do this by creating a separate plot for each x-axis column required. However, after setting this up for a bunch of plots you may need to make a simple adjustment that now needs to be done for every one of these plots.
You could also do this by switching the x and y axes so that the responding variable (gas EUR or oil EUR) is on the x-axis and the multiple manipulated variables are on a single y-axis, then plot using trellis by column names. However, it is highly unconventional to plot the responding variable on the x-axis. Furthermore, in many cases you want to do this for both oil AND gas EURS, so it would make things very simple and convenient to be able to have 2 (or more) x-axis columns and to trellis column by y column name and trellis rows by x column name, giving you an n x 2 grid of plots that shares a single color by, shape by, size by, etc.