Limiting certain content modules to one per array in a Sanity.io project.

i have an array of different content modules that make up the pages of a website. most of the modules can be repeated freely throughout a page, but there are a few modules that i'd like to limit to 1 per array. assuming this would be done using

custom

validation? has anyone done this?

not very sure about this but I think can be a solution. This limits the document or object to be updated and published but not created or deleted. I believe it removes the create and delete buttons

this is usually used with siteSettings which is usually used once through out the site

this isn't quite what im looking for

i think i solved the problem thank you!