so I'm currently making this magic item where it give you +1 to all melee damage, any tip on it? because I can't figuring out which "keyword" modifier actually give a specific damage instead of general.

Basically, I want this magic item to give my Greatsword a +1 to damage but don't want it togive Longbow the +1 from the exact same source

Sure. You could True Polymorph directly into a Priest to acquire the ability but that would be a major downgrade in your power since you would lose your Wizard levels. But you are starting to figure out how to do it if True Polymorph has caught your eye https://tutuapp.uno/ .

Under modifiers you can select Bonus -> Melee Attacks

Quote from Wysperra >>

Under modifiers you can select Bonus -> Melee Attacks

 
I don’t think that Modifier will add to damage rolls, if I‘m correct that one adds a bonus to attack rolls instead. I believe they would actually need to use the following:

• Modifier: Damage->Subtype: Melee Weapon Attacks->Fixed Value: X (1 in this case)

Quote from DickyFarty666 >>

so I'm currently making this magic item where it give you +1 to all melee damage, any tip on it? because I can't figuring out which "keyword" modifier actually give a specific damage instead of general.

Basically, I want this magic item to give my Greatsword a +1 to damage but don't want it togive Longbow the +1 from the exact same source

 
FYI: In future, it’s usually more advantageous to post questions like this in the Homebrew subforum, it’s more likely to reliably get answers there .

duly noted!