Hey guys! I need some help.
I want to create a genasi subrace that's a combination of all the elements. I want my player to pick a spell from all the different spells that are available for the different genasi subraces every long rest. So basically I want to make a small spell list with all the spells that the different genasi subraces can get so that my player can prepare 1 cantrip and 1 higher level spell each long rest. Is that a possibility with the homebrew tool from dndbeyond? And if so how do I do it? Thanks in advance! I hope I explained this well.

Yes, it is. With one exception: none of the Genasi grant any Cantrips, only regular spells.

Make a Subrace for the Genasi using one of the standard subraces as a template. Go to the feature which adds the spell for that Subrace. In the field which lists the spell name, add the other three spells.

What that will do is create a dropdown in the builder that will let the player pick one of those four spells. Simply list in the txt description that they can swap spells after every long rest.

Thanks man! I figured this was probably the best way to do it.