As the title said, I'm trying to create a weapon in the homebrew section to give a player. The weapon is a normal +1, but when attacking aboleths and mind flayers it's +3 and when attacking kuo-toa it's a +4. Unfortunately when I went in and did all that, the character sheet has now added all those together into a +8 sword. No discrimination toward a specific monster type. 

I do not know how to do this without them combining like that. Is there a setting or drop down I missed? Or is this not possible?

The builder isn't smart enough for conditional features like this.

The system has absolutely no way of knowing what type of creature you’re player’s character is going to attack on any given roll, so it can’t do that.

I wasn't really hopeful of it having a way like that. But I wasn't looking for a system to be able to tell what monster the players were fighting. I was looking for more of like a seperation of the bonus magic similar to what a versatile weapon had for one hand vs. two hand. But I guess what I'll have to do is just make 2 additional copies of the weapon with no attunement so they can sit up in the actions menu with the appropriate hit and damage. 

It's annoying that the system let's me just add additional bonuses as if it does have a seperation of them, but whatever. 

Yeah, that’s why they have the system for customization on the character sheet, so players can manually adjust that stuff.