One way to accomplish this would be to use the Fields Calculator.  (Right click on "Field Overlays" in the Project Manager Menu and then click on the Calculator.)  Then, you can take the appropriate scalar component of the J Quantity and integrate it over the plane.  To access the result, you can create fields report and find the expression you created under the Calculator Expressions.  (Note that to actually be able to access the results you will need to make sure that you are saving the fields solutions.)


Depending on your geometry another possible approach (for a transient simulation) might be to create a winding with the plane as the only coil terminal in the winding.  Then you can assign a zero voltage excitation to the winding and plot the current in the winding.