Based on what you mentioned, my understanding is that your client was a NYS tax resident.

You can't force zero flow-through from the K-1.  That's not how it's supposed to work.

It is anticipated within the legislation and tax return design that everything will flow through to IT-201 like any regular K-1.  The shareholder would then make the necessary adjustments on IT-255 to add to and subtract from Federal AGI to reverse those flow through items.  Lastly, the shareholder would add back actual distributions that should be subject to tax based on the S corp being treated as a C corp for NYS tax purposes.

Edit: You can find the modification codes in the filing instructions for IT-255.