SharePoint Search - how to add '*' character to search??

MarioZagreb SharePoint search is pretty straightforward. It will search the title, metadata and text for EXACTLY the string you enter. If you enter ABC in the search box, it will search for that string EXACTLY, discounting certain characters like space, dash and underscore. If your documents only contain ABCD or ABCF or ABC1, those do not match so will not return. If you want to find ALL variants that start with ABC, then you have to add *.  This is normal search functionality - nothing different from Google or any other search function. 

So in your screenshot below, I would expect search to return "aaa - copy.pdf" but not necessarily expect to see "aaay.pdf" unless you add *.

Also, when testing stuff like you're doing below, remember that search is based on an index crawl. If you add a document NOW and immediately search for it, it, probably won't appear in the results as the crawl hasn't had time to index the document - which may explain why your document didn't show up as you expected. Give it a few minutes, sometimes as much as 30-60 minutes for it to respond properly, particularly if you are expecting search to return results based on document contents.

Generally speaking, I would NOT recommend messing with default functionality. This is DEFINETLY an area of "Law of unintended results". You're using fairly simple search terms in a small, contained test environment. But think bigger. Once there are 1,000 documents in the library, maybe your users don't want EVERY document with every variant of the word "engineer" (engineering, engineered, engineers, engineerified, etc.). Or if they do, then they can add a *. If you re-write search for them, you are removing that element of choice. This could go very wrong.

Lastly, if you're specifically focused on metadata, maybe try filter instead? Then you find all the values want. You can even add columns to the filter pane to make filtering multiple columns even easier.