I'm trying to make a new weapon type in the Homebrew creator but can't seem to figure out how. 

The weapon is called a Striker. It's basically just an exact copy of the Scimitar but it does Bludgeoning damage. It's meant for a non-Monk character that wants to punch things but not be at a complete disadvantage compared to Weapon builds. 

How do I make it?

I've tried making a copy of a Scimitar as a magic item, but there's no place for me to change the damage type and it always displays as a Scimitar. I've tried using a Mace as the template but there's no place to change the Properties, Mastery, or make it a Martial Weapon. Is this even possible on D&D Beyond? 

Yeah, that's impossible on d&d beyond. You may be able to copy the mace and add finesse and light to it, but for some reason you cannot create custom weapons. The 2024 monk is really good though, so I don't see why you need a weapon so that monks can use bludgeoning damage, just use fists or light hammers.

Just tell them to use.a Mace and rename it "Fist" and flavour it as punching.

Quote from StereotypicalDungeonMaster >>

Yeah, that's impossible on d&d beyond. You may be able to copy the mace and add finesse and light to it, but for some reason you cannot create custom weapons. The 2024 monk is really good though, so I don't see why you need a weapon so that monks can use bludgeoning damage, just use fists or light hammers.

It's not for a Monk. It says that right in the post. 

Monk might be good with punches but literally every other class is worse off by using unarmed fighting because of how to compares to Dual Wielding with Nick or using a Heavy weapon with GWM. And multiclassing Monk requires Wisdom and the Martial Arts feature requires being unarmored. So if you want to punch stuff, either go Monk, which has a very specific fantasy, or play a different game. At least that's the official DND stance on it. 

Quote from Agilemind >>

Just tell them to use.a Mace and rename it "Fist" and flavour it as punching.

 If I was willing to just re-flavor something I wouldn't be asking how to do it on the Homebrew section of the Forum. 

But when your Pirate Ship finds the gold let me have a piece or two Captain Obvious. 

Quote from Jaymezz149 >>

I'm trying to make a new weapon type in the Homebrew creator but can't seem to figure out how. 

The weapon is called a Striker. It's basically just an exact copy of the Scimitar but it does Bludgeoning damage. It's meant for a non-Monk character that wants to punch things but not be at a complete disadvantage compared to Weapon builds. 

How do I make it?

I've tried making a copy of a Scimitar as a magic item, but there's no place for me to change the damage type and it always displays as a Scimitar. I've tried using a Mace as the template but there's no place to change the Properties, Mastery, or make it a Martial Weapon. Is this even possible on D&D Beyond? 

Not sure why other people say it can't be done but there's a modifier for Replace Damage Type that does the thing you want it to do. Give this a read on most everything about homebrew weapons including multiple examples of flavoring different types of weapons. My examples customize every single damage dice combination into a light, finesse, radiant damage laser sword.

I do not go into weapon mastery as it wasn't a thing then and I haven't looked into it much since they rolled it out last year.