By looking into the inner workings of PCGen, I have manage to cobble something together that seems to do the trick. However, this answer is in no way comprehensive, but meant to serve as a guide on how to patch your own homebrew stuff. For more information about working with Homebrew files, I suggest looking into the documentation (Help -> Documentation, F1), under the "List Files" heading (Sadly, I cannot link to specific pages of the documentation here).
[PCGen]/data/pathfinder/homebrew/my_homebrew. This is the pre-installed Homebrew Campaign Thingy, which will do just fine for this purpose.
Traits are internally handled as "abilities". Using a good text editor (Notepad++ or similar), open up
#insert your data here, add the following line
Homebrew Trait KEY:Trait ~ Homebrew Trait CATEGORY:Special Ability TYPE:Trait.BasicTrait.CombatTrait PREMULT:1,[PREABILITY:1,CATEGORY=Special Ability,Trait ~ Homebrew Trait],[!PREABILITY:1,CATEGORY=Special Ability,TYPE.CombatTrait] DESC:You have studied the workings of PCGen and managed to claw your way into creating a homebrew trait|PRERULE:1,DisplayFullAbility NATURALATTACKS:Claw,Natural.Weapon.Melee.Finesseable.Piercing,*2,1d4
Let's look at this line more nicely formatted:
Homebrew Trait KEY:Trait ~ Homebrew Trait CATEGORY:Special Ability TYPE:Trait.BasicTrait.CombatTrait PREMULT:1,[PREABILITY:1,CATEGORY=Special Ability,Trait ~ Homebrew Trait],[!PREABILITY:1,CATEGORY=Special Ability,TYPE.CombatTrait] DESC:You have studied the workings of PCGen and managed to claw your way into creating a homebrew trait.|PRERULE:1,DisplayFullAbility NATURALATTACKS:Claw,Natural.Weapon.Melee.Finesseable.Piercing,*2,1d4
- It starts off with the name of the ability, "Homebrew Trait"
- Next up is the
KEYkeyword, followed by the internal name of the trait, allowing you to use this trait in other homebrew things, as a prerequisite for a feat, for example. I followed the naming convention I found in other
CATEGORYtag is there to list this under Special Abilities, nothing much to say here.
TYPEtag is more involved. This is a dot-separated list of subcategories this Special Ability falls under. In this case, we have a trait which is a basic trait, and which is a combat trait. You can change the latter to what you like, but you'll have to change the prerequisites as well.
- The line starting with
PREMULT:1states that only one of the following prerequisites need to be fulfilled. The prerequisites are given in square brackets.
PREABILITY:1,CATEGORY=Special Ability,Trait ~ Homebrew Traitmeans that you qualify for this trait when you have this trait. In particular, it means 1 prerequisite ability from the Special Ability category, which is "Trait ~ Homebrew Trait". This is needed because of the second prerequisite.
!PREABILITY:1,CATEGORY=Special Ability,TYPE.CombatTraitmeans "Not 1 Special Ability pf the
CombatTraittype, as per the trait rules. Without the first prerequisite, this would make the trait disallow itself.
DESCis followed by the full description of the trait. Not sure what the
PRERULEpart does, just keep it there.
NATURALATTACKSadds the crunch. I copied this part from a Tiefling Alternate Racial Trait. It adds an attack called "Claw", lists the applicable types (see above), makes it 2 attacks, and sets the damage to 1d4.
Once you have written up your ability to your liking, save the file and open up PCGen. Go To Sources -> Select Sources (CtrlL), and go to the Advanced tab. In the dropdown list at the top, select Pathfinder RPG as your Game. On the right side, you should now see "Pathfinder RPG for Players", as well as "My Pathfinder Campaign". Click on Load. Your homebrew trait should now be available to choose from the list of traits.