Yes, many thanks Ilian for your answer! I used this approach many times. To my surprise, in Mathematica V14.1 there are quite a lot different folders – and many other "MenuSetup.tr" files. For my purposes, with Windows 11 environment, I had to find the right one first. The upper directory tree (here: C:\Program Files\Wolfram Research\Wolfram\14.1\SystemFiles\Components\Mathematica\FrontEnd\TextResources) divides into at least three almost identical sub-directories: "Mac", "Windows" and "X" and a few more.

In my case, the actual "MenuSetup.tr" file is contained in

SystemOpen[
 FileNameJoin[{$InstallationDirectory, "SystemFiles", "Components", 
   "Mathematica", "FrontEnd", "TextResources", 
   Switch[$OperatingSystem, "Windows", "Windows", "MacOSX", 
    "Macintosh", "Unix", "X"]}]]

But then everything works fine. I use "F8" as Andreas suggested.

I have the same problem with Mathematica v.12.0 running on Windows 10. The only solution I found is to **Insert** -> **Insert Free-form Input**

Thanks a lot to Andreas for putting forward this problem and to Ilian for solving it. I had the same problem with a Norwegian keyboard and accepted it didn't work in the previous versions. But now it has become a more important feature in version 10 and short cuts for free-form input should be available on all key boards. The quick fix is registered and appreciated, but a real fix is needed next time.

The shortcut can be changed by modifying the file

 FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrontEnd", "TextResources", 
      Switch[$OperatingSystem, "Windows", "Windows", "MacOSX", "Macintosh", "Unix", "X"], "MenuSetup.tr"}]

Specifically, look for

MenuItem["Inline Free-form Input",
         KernelExecute[AlphaIntegration`LinguisticAssistant[InputNotebook[]]], 
         MenuKey["=", Modifiers->{"Control"}], MenuEvaluator -> "Local"]

Hi, CTRL + SHIFT + 0 doesn't work; this was my first try. Any other ideas?