I remember seeing a view in Seller Central under “Add Products” where I could type a keyword and get a list of products showing whether or not I’m eligible to sell them. Is there still a way to access that view?
Yes, that view still exists but Amazon has moved things around a bit, so instead of going through “Add Products” directly you now need to go into Catalog → Add Products in Seller Central and type your keyword or ASIN in the search bar.
It will show you the existing catalog listings along with whether you’re eligible to sell them and, if not, whether you can request approval. Sometimes Amazon hides that search if you’re in the wrong marketplace, so make sure you’ve switched to the right region (US, UK, etc.) before searching. Another way to check eligibility is through Inventory → Add a Product where the search bar behaves the same way, but the results page layout looks a bit different than it used to.