Before you plot the energy levels, you need to create the groups of the energy levels what you would like to see in a single figure. After uploading the MARVEL energy file, you can select the column(s) of the quantum labes what create a group. For larger molecules, a group can be created more than one quantum labels (using the 'with' button).

For example:
Let's suppose you work on the water molecule. The quantum lables are: v1 v2 v3 J Ka Kc, and you want to see the energy levels in the function of Ka for the different VBOs and for different J values. In this case, the group 1 should be the column 1, 2 and 3 (using the 'With' button, these are the v1, v2, abdd v3); create a new group, and group 2 should contain the column 4 (this is column of J). Check the 'Select column to x-axis' and choose the column 5 (this is the Ka). Click 'Show table'. Click on that 'Show' button in the table what you would like to see.