I have created a "feat" for my warlocks. Allows a number of *always prepared* patron spells that you can cast once per long rest or using your warlock spell slots. 

In the homebrew feat creator > Add Spells > I have selected the possible "patron spells" that I can choose from the list, and choose CHA as modifier;  put # of use : 1  Resets on : Long Rest. I check the box "Is Infinite" at the bottom, so player can choose multiple "Patron spells" (based on his warlock expanded spell list table). 

In the Manage feat section of the character sheet, I select the "feat" (called "* Warlock Patron Spells") and choose my given patron spells from the drop down lists. 

They now appear correctly in the spells section, with a "Use" button.

When I click on "Use", I get this "Beholder!" error:

Whoops! We rolled a 1 on our API check. We're heading into town to visit the blacksmith for repairs.

Try again after a Short Rest.

Update: so, I have tested this with only two spells as options (instead of the 50+ Patron Warlock spells)... If the "Is Infinite" box isn't checked -- i.e., you only get one of the spell options added to your character sheet -- it works.  As soon as the "Is Infinite" box is checked and you can select multiple spells with the same feat, the error message appears when try to "use" a spell.  

Thank you for addressing this bug so we can have the option to select multiple spells that reset 1/long rest. 

Support team?

Here 's the link to my homebrew feat (not public) : Warlock Patron Spells - Feats - Homebrew

(This version only has warlock patron spells for 1st and 2nd level, but the bug/error message is there no matter how many spells are included in the builder's spell list box)...

The "Is Infinite" box is ticked to allow multiple spell selection directly from the Manage Feats section on the digital character sheet as the warlock character goes up in level. 

You can select the spell, and the "Use" red button correctly appears beside each selected spell, but pressing the Use button gives you the aforementioned error (first post in this thread)...  Somehow, the current coding of the feat builder doesn't like when there are multiple spells selected with a 1/long rest attribution...

Thank you for your help.

Two things:

1. There is no “manage homebrew” section of the digital character sheet. Are you perhaps using an extension such as Beyond20 to port the sheet into a VTT like Roll20?
2. The “Is Infinite” checkbox will always throw that error whenever you use it to grand spells that can be cast like that. That checkbox was created to support the Ritual Caster feat which does not allow a PC to “cast” its spells in the normal way or “use” them at intervals, only to cast them as rituals which requires no button. As long as you have that box ticked, you will always get that error. If you want the error to stop, you must untuck that box.

I am afraid that how you want that to work is currently impossible to program as a Feat in the homebrewer. The reason being that feats are not intended to have anything change depending on character level. They are supposed to be one-and-done whenever they get it no matter what level. To do what you want you will either need to:

• Incorporate your design into either a custom homebrewed Subclass or Race for that Character. You will still not be able to use the “Is Infinite” checkbox, but will need to add individual instances of “Add Spell” (one at each level) and each of those will need to have the entire list included.
• Create it as multiple feats that get added to the character sheet at various levels. 
• Use multiple instances of “Add Spell,” list every spell you wish to include as available for every instance, and instruct the player to only select one spell at each level and leave the rest blank in the meantime.

Sorry I can’t give you better news than that. I hope it helps.

Quote from IamSposta >>

Two things:

1. There is no “manage homebrew” section of the digital character sheet. Are you perhaps using an extension such as Beyond20 to port the sheet into a VTT like Roll20?
2. The “Is Infinite” checkbox will always throw that error whenever you use it to grand spells that can be cast like that. ....

 1. I meant "Manage Feats" on the digital character sheet, where you can add feats outside the usual ASI levels. 
2. I appreciate the feedback and the time it took to response. As a temporary fix, I had already created a feat with multiple instances of "Add Spell". Out of curiosity, are you part of the D&D Beyond team? There is no D&D Beyond tag beside your name, so I'm kind of confused if your answer is definite or can I still hope for a fix from a DDB staff member. I understand right now, it cannot work, but there is no reason something you can do with the feat builder (available options) should give you systematically an error message. At the very least, the option to select "Is Infinite" should be grayed out when not possible to use...

I am not now, nor have I ever been affiliated with DDB in any capacity other than as a site user like yourself. (I don’t work here, I just live here. 😂) However, I do use the homebrewer extensively, in fact I probably spend more hours fiddling around in there just to see what it can do than the average Dev spends in there in any given week. While I wait for things to update I surf the forums and answer questions like yours.

DDB is currently revamping the content creation software, but since I am not a part of the team, I have no clue what’s being done, the order in which things are getting done, how much progress has been made, or any insights on an ETA.

You can use the “Is Infinite” function, just only for Ritual Spells.

What you have to understand is that the homebrewer isn’t actually a “homebrewer” at all. It is the exact same system the Devs programmed for themselves to use when implementing official content into the system. The just stuck some functions behind admin access (which we don’t have) and opened the doors for us to use it. It was never actually intended to have a user interface that is convenient for the public to use, or easy for us to understand. It was really only ever designed for use by people who already understand it to do things that it was already designed to do. (There are reasons why, but it’s a long story.)

PS- As someone more than a little familiar with the content creation software, might I give you some advice? For what it seems like you are trying to implement, it would likely be much simpler to do as a class feature for each of the relevant Warlock subclasses rather than as a feat. With a single 1st level  class feature you could make it do exactly what you want it to do without the headache you are having trying to do it as a feat.

Quote from IamSposta >>

I am not now, nor have I ever been affiliated with DDB in any capacity other than as a site user like yourself. (I don’t work here, I just live here. 😂) However, I do use the homebrewer extensively, in fact I probably spend more hours fiddling around in there just to see what it can do than the average Dev spends in there in any given week. While I wait for things to update I surf the forums and answer questions like yours.

DDB is currently revamping the content creation software, but since I am not a part of the team, I have no clue what’s being done, the order in which things are getting done, how much progress has been made, or any insights on an ETA.

You can use the “Is Infinite” function, just only for Ritual Spells.

What you have to understand is that the homebrewer isn’t actually a “homebrewer” at all. It is the exact same system the Devs programmed for themselves to use when implementing official content into the system. The just stuck some functions behind admin access (which we don’t have) and opened the doors for us to use it. It was never actually intended to have a user interface that is convenient for the public to use, or easy for us to understand. It was really only ever designed for use by people who already understand it to do things that it was already designed to do. (There are reasons why, but it’s a long story.)

PS- As someone more than a little familiar with the content creation software, might I give you some advice? For what it seems like you are trying to implement, it would likely be much simpler to do as a class feature for each of the relevant Warlock subclasses rather than as a feat. With a single 1st level  class feature you could make it do exactly what you want it to do without the headache you are having trying to do it as a feat.

I think we have something in common. I don't spend as much time on forums as you do, but at one point, I was listed as the 2nd or 3rd person with the most homebrew stuff (public and private included) on D&D Beyond according to a dev update 😄. 

I figured we had access to whatever the D&DB team are using themselves, having seen only the "official" things found in published books as options in the builders. At the same time, they did mention they wanted to improve/expand the homebrew builders, and an option that ends up with an error message is one thing they could look at (for a fix, or a non-error solution). 

I do "revised" versions of subclasses, but things are pretty crowded in the character builder when selecting a class. I figured for the warlock I could get away with two "feats" for the fix (one expanding some warlock features, and the other one for these *always prepared, 1/long rest" patrons spells. And it does work. Instead of using the "Is Infinite" option (which prompts the error), I have created 5 "spells", selecting one relevant patron spell from a list of 1st warlock patron spells (resets on long rest), then one from the 2nd-level spells, and so on. 5 drop down options; player simply unlocks the appropriate spell as they gain warlock levels.

Thanks for the help, and see you around the forums 😁

As usual, happy to help. See you around.