I am making a homebrew subclass similar to Warlock's Genie. At 1st level you have multiple options, e.g. Fire/Water/Air/Earth, each of which grants different spells added to the class' spell list. So for option Fire, I want to add additional spells (A,B,C) to the character's spell list, but for Water I want to add different spells (X,Y,Z) and so on..

I can't figure out how to do this - additional spell list can be made only on feature level, not on an option level. Thru options I can only add spells, which are then automatically "known" not add them to the spell list from which the character can choose what to learn. If I were to create a feature for each option, so that I can add different additional spell list, I can't link whole feature to the formerly chosen option. Seems like I could make replacement features, but it would not be automatically selected and it would be up to the user to select the correct feature.

The only available option I can see right now is create a different subclass for each option separately. Is there a way to do this within one subclass? 

I wanted to link this thread here, it talks about the same thing but there are no resolutions https://www.dndbeyond.com/forums/d-d-beyond-general/bugs-support/135236-homebrew-subclass-access-to-a-different-class

The way they did it for the Genie Warlock was to add all the spells for all of the options as “Additional Specific Spells” under Basic Information and leave it upto the player to know which spells they can or cannot choose.

Thanks for the help :) Also, is there a reason why additional spell list is omitted in options when modifiers, spells actions and creature are not? It's a bit weird that a player has to remember such a thing. Seems a bit undone when those other functions are implemented.

Happy to help.

I can’t say for certain, but I suspect the reason that isn’t attached to Options is because the juice:squeeze ratio to program it is so low. Y’see, that Additional Spell List subform was added to the features form way after things got started, and it took them months of programming to do it. Adding it to Options would probably take even longer because the more things are nested, the more complicated they are to make work properly. Since currently the only thing that would use it is the Genie subclass, and since they currently have a workaround in place, I imagine it’s probably a pretty low priority for them at the moment.

I know this is quite old, but I'm working on something similar, making a Dragon patron Warlock, and wanting to do something similar to the Genie warlock, but having the spells automatically selected depending on the dragon/element you pick, instead of how the Genie is implemented where you have to know Marid doesn't get Burning Hands or whatever.

I am still actively working at it (so far, only done 1st and 2nd level acid spells) so there may be a better way, but this is what I was able to do to get an acid dragon spell list to show up instead of all options.

1st. Do not have any spells in the "Additional Specific Spells box of the main homebrew class. This will add those spells to all options regardless of option selected.
2nd. Make a class feature where you select your desired patron type. If making from scratch, be sure to add Class Feature Options below.
3rd. Make your Expanded Spell List class feature, and make a Class Feature Option below for each patron type you made in step 2.
4th. Select a prerequisite class feature option (In my case, I'm selecting Dragon Patron - Acid). This will make it so anything we add here will only be available if I have an Acid Dragon for my patron.
5th. Click Add Spell. Select one (1) spell you want your warlock to have access to at a time. I made the mistake of selecting multiple spells at once here. This won't give your warlock access to all of them, it will require your player to pick 1. Leave most options blank and untouched, but be sure to switch Consumes Spell Slot to Yes. If you want to have it as an option for your warlock (2014) then have Always Prepared as No. If you want your warlock to have it anyway (2024) then select Yes. Put the relevant character level where the character would be able to cast the spell, and hit save. Do this for each of the spells you want on the warlock expanded spell list.
ETA: I think if you're doing 2014 rules, you'd want it to count as a known spell, but I'm not 100% certain here. I'm adding these spells 2024 style to my subclass.

Hope this helps anyone else looking to make something like this!