Right now I'm in a cyberpunk campaign and since it's in the future, there are firearms.  However, dnd beyond does not have any kind of ability to create regular items unless they are magical, which frankly sounds stupid.  Not only that, trying to just add the gun to my inventory and then create a separate attack does not work for this as the guns in this campaign don't have proficiency or attribute bonuses to the damage rolls, which you can not have without also getting proficiency for attack rolls.  This could just be easily fixed by letting us create our own items and weapons instead of having to do this inferior way of using custom weapons.

 You can do this, just it's sheet by sheet. And yes, that includes choosing if it does or does not include proficiency, which stat to use, etc, or forgo stat entirely with custom damage.

Like this.

Now the char has +0 dex mod and I based it off dex, so the to hit would be +0 (I couldn't be bothered to make a new character so just used a test one I already had). But the damage is 1d6+10 , just that, no dex. And there's no proficiency. So it matches what you described.

It's just a custom action. 

For info about custom actions, custom items and other on-the-sheet customisations please see my video here:

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It's not ideal, but hopefully it'll help.

Quote from FeelsDankMan413 >>

Right now I'm in a cyberpunk campaign and since it's in the future, there are firearms.  However, dnd beyond does not have any kind of ability to create regular items unless they are magical, which frankly sounds stupid.  Not only that, trying to just add the gun to my inventory and then create a separate attack does not work for this as the guns in this campaign don't have proficiency or attribute bonuses to the damage rolls, which you can not have without also getting proficiency for attack rolls.  This could just be easily fixed by letting us create our own items and weapons instead of having to do this inferior way of using custom weapons.

 
I’m confused, no weapons add Proficiency to o the damage rolls. All you would have to do is manually adjust the attack and damage rolls for the laser pistol directly on your character sheet and it should do you.

It's not a laser pistol, it's a custom weapon.  If you're proficient with it you add your profiency bonus only to the attack rolls, not the damage rolls.  There's no way to make it so only your attributes and proficiency goes to your attack rolls but not the damage rolls.

Proficiency bonus is never applied to damage rolls. That’s just standard RAW for all attacks in this edition. The system will never add your proficiency bonus to the damage rolls.