When you build a story, you're an Author.
When you build a world, universe, or something bigger, You're a Creatrix.
The english term for this obscure profession was stolen from the disused language drawer by Jennifer Diane Reitz.
Professional Creatrices usually work freelance, spending time putting each interlocking part of the whole together perfectly; adjusting the speed of light just so; setting up the subatomics or whatever brand of particle they've licensed for the project; making sure the energy is budgeted properly. If humans are tenants, and gods are the landlords, they are the architects.
Sadly, gods rarely credit them after they pay, and pretend it was all their doing, and the most common method of retaliation is not giving away the complete manual.
Amateur Creatrices have more fun by focusing mostly on the most visible layer of existence, without actually doing the dirty work, and often steal a well known universe and lightly modify it. Usually by adding new rules and/or altering the state of the present.
Because the amateur Creatrix can rarely sell just the altered world without encountering copyright infringement lawsuits from beyond, all they can do with them is play with or share them, which is why most prefer to keep the new creation to themselves, and sell the stories of what happens inside.