So I'm tinkering with creating a homebrew sublcass for the Wizard class. At level 2, this subclass has a class feature that requires the choice of one of three options. I would like each of these three options to grant access to a different class' spell list: one would grant access to the Cleric spell list, one would grant access to the Druid spell list, and one would grant access to the Warlock spell list. Is there a way to set this up with DnDBeyond's Homebrew Subclass Creator? Here are the issues I've run into:

• While it is possible to add the additional class' spell lists (Cleric, Druid, and Warlock) in the "Additional Spell List" field in the "Basic Information" section of the Homebrew Subclass Creator, that would result in each of the 3 class feature options having access to all three additional spell lists instead of just the one that corresponds to the class feature option. Thus, this method wouldn't work.
• When editing one of the three class feature options, I can select "Add a Spell" and, within that selection, choose one of the additional spell lists under the "Spell Class" field. However, when the player is editing their character sheet, the additional class list does not appear in the "Spells" section of the "2. Class" tab. However, the additional spell list is present under the corresponding class feature on the same tab. Is there any way to make this additional spell list show up under the "Spells" section so that the player may select their spells from both spell lists at once—as opposed to only being able to select the additional spells from the class feature section?

I'd recommend that you take a look in the homebrew forums. There are many pinned guides there that can help you, one of which is in blue below. 

It would also probably be worth asking a Mod to move this thread to the homebrew forum. The people there will be able to help you.