Please create “Tag SKU” and “No Price” attributes first.

Special Attribute Catalogue

Then create a note SKU and check on the “No Price” checkbox (new attribute).

Service SKU, dynamic description or price

Finally, add the note SKU in the “Tag SKU” text box (the new attribute) of the SKUs which need the notes. If you have multiple note SKUs, use ; or , as delimiter for Tag SKUs. eg: SKU1,SKU2 (Method 1)