So apparently there is a autocomplete function with the TAB key, but it's functionality is only to find one possible alphabetic solution.

I think that feature does not really add much reason to use, except for if you know the commands well but type the word slightly wrong. A tab key can help spell out the command to correct the mistake.

That's not exactly where I am going with this feature request. This feature is meant to make commands more accessible, not to trial and error with tab or open the full list of commands. The tab key itself is also quite hidden, while a pop-up does it for you. If players can see the possible autocompletions and have some descriptions, it could be a huge quality of life feature.