d8 damage dagger

We found some daggers in our campaign, The only difference with them, is that do 1d8 damage. I have created one and set the "modifier" to reflect this, but in the inventory, it still says d4 and it does not save to save for me. 

It's not currently possible to change the base damage on a homebrew magic weapon.

What you can do is start with any of the weapons that have a d8 damage die already, and use homebrew modifiers to change its properties so it matches those of a dagger.

Okay, I was guessing I would need to do that. What is the "modifier" dropdown used for, for the different die types?

Quote from RighthAndyman618 >>

Okay, I was guessing I would need to do that. What is the "modifier" dropdown used for, for the different die types?

Which modifier are you referring to?

The die type?

I can't find where to edit the properties. I started with Rapier. I just need to add the thrown and piercing property. Piercing does already appear next to the damage type and Finesse and Vex are next to the Properties.