The instructions for limiting using the Curve Adjustment Tool in original PiezoDN applies to New Curve Output Contrast Tweaking section of PPEv2. The only difference is that (same as with any new curve) in PiezoDN you have to use QTR-Linearize-Quad to actually create the new curve, while in PPEv2 you just copy the New Curve as per the instructions.
Just follow the procedure in the manual but using Contrast Tweaking and you’ll be golden. Remember to put your Starting Curve in, but do not put in any measurement data. Shape the new curve with the 5 points exactly as you would in Curve Adjustment (except that you have 5 points rather than 4). Instructions for saving the New Curve are at the top of that tab in PPEv2.
Another option is to use the Start Points section of PPEv2 and set the highlight point to the new value determined from the results of printing the Limiter target, but this has the side-effect of lowering Step 1 density as well as everything else, rather than from step 2 onward. You could then go in and manually restore the higher step 1 density in the K channel, which I have done when using this tool.
I also remember Walker once musing on the possibility of having a check box to do that — maintain the high Step 1 edge masking density, maybe it wasn’t possible to implement that idea.
If you still don’t understand the process (which is not uncommon when you haven’t done it before), post the result of your Limiter print and I’ll walk you though it step-by-step.