Hi Fad, If you are using the D&D 5e 2024 by Roll20 you can give NPCs a second, third, etc damage type by switching from the statblock view to one of the other views, then edit the attack. Then switch back to statblock view when you are done. The inline editing is intended to be "simple". For more comprehensive changes you need to switch views. If that is not the sheet you are using please provide either the name of the sheet or a screenshot for identification.