Hi all, I wanted to create a Great Weapon version of the Dueling fighting style as a feat to add to a character or part of this homebrewed subclass. Basically to add a +1 to attacks delivered by a weapon wielding two hands. I'm not sure if this is currently possible or not but what I'm mainly interested in is the code as a homebrewed feat that adjusts the condition of "two handed weapon attack", similar to how the Dueling fighting style adds bonus damage to one handed melee attack. I know under "Damage" there's a setting called "Melee Weapon Attacks" but is there not a code/setting specifically for two handed weapons? 

I will direct you towards the Homebrew section of the forums. There are people there who know the homebrew creator tools better than the staff of DndBeyond. There is a tutorial about making homebrew feats that may have something like what you've described but if not you can ask there and someone will almost certainly be able to help you.

Thank you! I'll repost there and see if I can find it there. 

I can save you the trouble. Short answer, no.

Dueling uses:

• Modifier: Damage->Subtype: One-Handed Melee Attacks->Fixed Value: 2

It doesn’t add the bonus to the attack roll, it adds the bonus to the Damage roll. The Fighting Style that adds to Attack Rolls is Archery:

• Modifier: Bonus->Subtype: Ranged Weapon Attacks->Fixed Value: 2

However, there is no modifier subtype for “Two-Handed Melee Attacks,” at least not attached to the Bonus modifier which is where you need it. You would have to put it in plain text and the player would have to adjust their attacks directly on their character sheets.