@J8kes the tricky part of this is that Webflow’s API doesn’t have a search endpoint so matching up the collection item to a slug is tough. I think using the webhook method on collection item creation to send the id out and return it to a field on the collection itemmight be your best bet. As @Jeandcc posted in this thread you could do that with Zapier or any sort of web application framework (i.e. Flask).
If Webflow had a search endpoint on the API this would be much simpler, but I’m not sure of another way to do it. I suppose you could call the Get All Items in Collection endpoint and then wade through the response to search the slug and find the id, but once you hit over 100 collection items you’ll have to deal with pagination.
If anyone else has a simpler method I’m all ears.