Hoenstly it sounds like you want to add your own custom note to the weapon instead. I would recommend using the adjustment called "
Weapon Elemental Dmg, Custom". You will find this after you turn on "
ShadowChemoh's Adjustments".
I know it sounds strange but hear me out. Select the natural attack and in the duration where it says "
+1d6 elemental" change it to something like "
plus poison DC10" or whatever you would like. That will extend that wording to the end of the damage of the weapon.