Im working on a 300 page catalog with tons of "items" on each page. The information in the catalog is also put on a separate InDesign document for a "spec sheet" and sometimes, price sheets or flyers etc. I'd like to know if there is a way to find all InDesign documents with the same "item" on it. So if I have an edit in the catalog, I can be alerted to change the other documents. Im thinking this would also help in creating an index in the back of my catalog? If I could link all documents together so that if one is changed it would change the others but I think I need a genie in the bottle for that!
You might be able to use InDesign's book feature. This will allow you to group all of the related documents, and the InDesign index features can create an index that includes all of the documents in a single book.
It also allows you to easily open all of the documents included in a book, by opening the book file (which has an .indb extension), highlighting all of the documents in your book, and double clicking on one of them. Once all of the documents are opened, you can run search and replace functions and use the "All documents" option to change the elements that need to be changed in all of your individual documents.
@GoofyMonkey's comment reminded me of another option--placing your items into a Creative Cloud library. I haven't used them much, so I can't attest to how well this functionality works, but the idea is that you create an item in one InDesign document, add it to your library and then take it out of the library to add it into a second document. If you have to make a change to that item, make sure to update the version in your library, and when you open any documents that also include that item, you will be notified that the item has changed (I imagine it might show up in your links panel just like when a linked image is edited).
You can definitely also combine the two--place all of your documents into a book file (for keeping track of which documents are related to which other documents, and index creation) and then use the CC libraries for placement and updating the items.