It is a known issue that if you create an index within Console, or add a new field to an index within Console, the syntax helper doesn't recognize these new entities for autocompletion. The workaround for it is to refresh the browser page, and when Console reloads, it will re-read mappings and then know about them. Reloading won't lose any work because Console saves the state of the editor in browser local storage.
If the problem is not happening because of that scenario, do you have any more information you can share, such as what are the specific terms not being autocompleted?