I'm making a homebrew creation, how do i add bonus weapon and skill proficiency in the builder?

Modifier: proficiency, modifier subtype: the weapon or skill.

Hi Starscream! You will want to use "Modifiers". These will let you add "Proficiency", and you can then choose which proficiency is gained. You can add another modifier for each additional proficiency being granted.

I hope that helps!

I am having some issues with this. I added the proficiency with heavy armor to a homebrew subclass using the modifiers and proficiency and heavy armor and it’s still not showing up on their character sheet. Sometimes I had to delete the class from their character and re-add the class but it’s still not showing up. 

Please see the General Homebrew FAQ #s 6: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq). If that doesn’t sort you out post again.

I'm making a 1st Level Feat that makes the player choose an INT based skill of their choice, and if they have proficiency they get expertise in said skill. How should I take care of that? make it like options to choose from and work from there?

Unfortunately you cannot. You would have to make a separate feat for each skill proficiency, and then do it again for each skill expertise. The system sucks eggs when it comes to Options on Feats.

Oh ok. Then, how would I reference each of them then, in case if 1 has proficiency in said select skill, then references the skill expertise 

Is this for publication, or for your private game? I would suggest not attempting to publish it because of how convoluted you would have to make it and the fact that each feat could not refer to any of the others with links. Just make it for your private use.

Oh no! It's not for publishing at all. Just for testing/private purposes. I guess I'll scrap the idea (since testing it would be outrageous). Thanks again.

I wouldn’t scrap the idea, I would just only make the version I needed to for my player is all.

So the idea I want is silly but I am trying to make a homebrew proficient in a homebrew magical item, are they already proficient in those or am I doing it wrong? It isn't letting me select the ite I made

Okay. You’re butting up against 2 separate but interrelated problems:

1. We cannot make “basic equipment” on DDB, only “magic items.”
2. Any “magic items” we create are assumed to be based off of preexisting basic equipment covered by the standard proficiencies.

So there’s no way for you to make anything that would grant proficiency in something you invent in your game like that. It would be better to add a “custom proficiency” directly to the character sheet. It’s actually easy, just click/tap the little cog symbol (⚙️) under the proficiencies section of the character sheet and simply add the proficiency.

Is there a way to give a list of choices as opposed to granted proficiencies? For example, I'm trying to homebrew a class that gives proficiency in Persuasion and proficiency with your choice of three types of tools. I have one modifier that grants the Persuasion proficiency, but the second modifier is what I'm struggling with. In Modifiers->Proficiencies I can choose "Choose a Tool" or "Choose Artisan's Tools" but I want to limit the choices to a specific three (jeweler's, painters, or calligraphers) rather than all Artisan tools. Is there a way to do that?

Quote from royalzugzwang >>

Is there a way to give a list of choices as opposed to granted proficiencies? For example, I'm trying to homebrew a class that gives proficiency in Persuasion and proficiency with your choice of three types of tools. I have one modifier that grants the Persuasion proficiency, but the second modifier is what I'm struggling with. In Modifiers->Proficiencies I can choose "Choose a Tool" or "Choose Artisan's Tools" but I want to limit the choices to a specific three (jeweler's, painters, or calligraphers) rather than all Artisan tools. Is there a way to do that?

Yes. Please see the Homebrew Subclasses & Species FAQ #19: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq).