How to declare a custom type in Sanity.io schema and resolve the issue

Hey everybody! Sorry to bother you all but I have an issue I cant figure out, even tho I know the solution is probably simple, and I'd like some guidance if possible:

How do you declare a custom type? For example in the Personal-Website-NextJS template, they have a custom type of "timeline" and "milestone", I want to understand how to do this but I keep getting errors :(

https://www.sanity.io/docs/schemas-and-forms
through the schema you can add custom types if I understand you correctly.

in the first example schema on this page it shows creating a new type called "person"

Just checked your link out. No, that's not what I was looking for.
Let me explain with this:
https://www.sanity.io/docs/schema-field-types (scroll down to the 4th code block)They didn't explain much on how they made the "accessibleImage" type or how they got it to work.
That's where I'm stuck .

they define that in the code block just before it

yes but when I reference it, I get an error that its not an appropriate type

Unknown type: timeline.
Valid types are: settings, array, block, boolean, datetime, date, document, email, file, geopoint, image, number, object, reference, crossDatasetReference, slug, string, telephone, text and url

have you included that type in your schema?

you need to import that type into your schema index file and add it to the array for it to be available

let me try again

ooof, it works now. thank you so much!I guess I was overthinking it. I assumed that 'objects' cant be referenced in the schema index, only 'documents' can. It's appearing and working fine now
🙂

🙂 yeah everything you define in the schema needs to be in that schema array, objects and all. glad you got it working 👍