I was messing around with the Homebrew options when I discovered there's some limitations to the Homebrew customization.  Specifically, I was creating races for my homebrew campaign and can't create custom languages for those races to speak.  Also, I couldn't find a kilt to outfit on one of my re-created characters so I went to add a homebrew *mundane* item.  No luck there either, so I tried to create a non-magical *magical* kilt, but was restricted by item types.  Any chance we can see these things added in the future?

You can have your character's clothes look however you like. But, no, they do not plan on allowing homebrewed mundane items.

Custom languages can be added directly to the character sheet.

Mundane items such as clothing have never been part of D&D 'rules' per say. If you want your character to wear a kilt, you say "My character is wearing a kilt". You'll notice there's likewise no item for a skirt, shorts, trousers, leggings etc.

Indeed, but there are "outfits" like "Clothes, Common"...but didn't realize there was a way to add other equipment to my character sheet.  As for the languages, I was looking for a one stop shop for my players, so when I create things like "Human (Irish)" race, they can have specialized "Irish" language and I wouldn't have to tell my players to change languages on their sheet, it would automatically be added when they select that race.

I mean, players generally make a character once, so they'd only have to add that language one. Language is a 'single entry' item in that you enter its name and that's it. There's no metadata. No single entry items are homebrewed in the same as magic items; skills, proficiencies, languages. They're all just a single line of text.

Also, are you trying to homebrew real world settings into D&D? Kilts? Irish?

LOL...not exactly "real world", just analogues...I was just using "Irish" as a theoretical example of what I was trying to do...