Mixed race from half-elf and half-dwarf

I’m creating a character and looking for help on how to go about applying racial traits. My character’s father is half human, half dwarf and her mother is half-elf.

I’ve only been playing for maybe two years, so I’m still new at this somewhat. I’m not creating a homebrew race just yet. I want to see how this character works out. I’m still learning about D&D.

I understand that the character would be 50% human and 25% of each of the other two. I’m unsure how to figure out which racial traits and what ability modifiers to use if.

Is there any guidance in the rules on how to approach such a racial mixture?