In Windows, LO Calc presents only a single function suggestion when starting a cell with the `=` character. When the user types “=co” Calc shows only COUNTIF(). I tried using the arrow keys, tab, and other ideas to coax other function suggestions out of it (such as CONCATENATE) but I could not get LO to show the other possible completions. The user expects that Calc will show a complete list of available functions matching the text, and that the user could select one with the arrow keys.
Tested on Windows 8 with LibreOffice 4.1.
Currently in LibreOffice Calc 18.104.22.168 there is no autocomplete / suggest / predict functions. The reason you might see COUNTIF suggested is because you already used such function and it is listed in the "Last used" functions category. To see those "last used functions", you could open the function wizard and select the first "last used functions" category.
This could be an enhancement request, but not a bug.
Changing summary description to reflect feature request.
And marking as 'NEW'.
*** Bug 71778 has been marked as a duplicate of this bug. ***
Meanwhile implemented with a tooltip presenting a collection of functions that can be travelled using Ctrl+Tab