Hello there!
The reason you are struggling is that what you are looking for isn’t available in Grist, at least not yet. There have been other requests for it. Multiple overlapping wishes are summarized and linked in More context in autocomplete results · Issue #249 · gristlabs/grist-core · GitHub. There is a chance this will get implemented before long. There are some design proposals floating around.
Meanwhile, one workaround suggestion that may work for you too is described in this response to a similar request: