This is my first time uploading home brew to dndbeyond, I've almost finished I just need one more question answered,

The class I'm making is a revised onomancy wizard and at 14th level, they are able to choose a name from a list of names that give them various bonuses, I've set all of the possible names as class feature options but I'm not sure how to make it so that the person can make the choice at the end of a long rest to change the name or keep it, right now I'm stuck in a rut where you make a choice in character builder and then you're stuck with it. 

No, they just have to go to the character builder to switch their choice.

Do yourself a favor, don’t publish it for a little humor until you have playtested and edited your subclass.

Thank you! this is actually a subclass I made when Onomancer was still active, its been thoroughly playtested, I just wasn't using dndbeyond at the time, do you know if there is a way to break the limit of 20 on stats? because that is also part of the ability, (there is an option for each stat to increase it by three, that way, the wizard can't be stronger than a barbarian) but it never shows up in sheet...

That requires two separate modifiers per Ability Score:

1. Modifier: Stacking Bonus->Subtype: [Ability] Score->Fixed Value: N
2. Modifier: Bonus->Subtype: Ability Score Maximum->Ability Score: [Abil]->Fixed Value: N

The first modifier generates a bonus actually capable of exceeding 20, the second actually raises the maximum.

Thank you! I was just able to finish! i really appreciate all the help!

Happy to help.