Can I enter a different x-axis column for each data set (e.g. participant 1 and participant 2) on a graph with multiple data sets while editing/writing LabTutor experiment in LabAuthor?

It is the limitation of the software that you cannot enter a different x-axis column for different data set in the same graph. The x-axis column has to be common for all data sets and the y-axis column must vary for different data sets (e.g. participant 1 and participant 2).