Upgraded to the newer version and got disappointed about the new icon. Maybe it is just me.
I will try replacing it with the ResourceHacker.

File associations are registered under HKEY_LOCAL_MACHINE\SOFTWARE\Classes for all users of a machine and under HKEY_CURRENT_USER\Software\Classes for the current user. Windows combines these two registry keys with current user file associations taking precendence over the local machine file assocations to HKEY_CLASSES_ROOT.

Let us assume a user associated via the graphical user interface of Windows the file extension .nfo with UltraEdit which could be done also in a command prompt window by running the following two command lines:

assoc .nfo=UltraEdit
ftype UltraEdit=^"^%ProgramFiles^%\IDM Computer Solutions\UltraEdit\uedit64.exe^" "%1"

The .nfo file association is stored in the Windows registry as follows:
The file association is registered either in registry hive of current user or in registry hive of local machine depending on the user used own account with write permissions only for HKEY_CURRENT_USER\Software\Classes or a local administrator account with using an elevated execution environment (run as administrator) for having write access also to HKEY_LOCAL_MACHINE\SOFTWARE\Classes.

Most users create a file association via the graphical user interface of Windows. There are several possibilities which I do not describe here as they differ from Windows version to Windows version although they all result in the same actions in Windows registry.

How to change the icon associated with a file type depends on how the user associated a file extension. Let us assume the user does not have the permissions to run Registry Editor of Windows as administrator and wants to change the icon for a file type.

The user has to open a command prompt window and run the command assoc with the file extension which is in this example: .nfo

assoc .nfo

The Windows command assoc outputs the associated file type registration which is the default string value of HKEY_CLASSES_ROOT\.nfo.

.nfo=UltraEdit

The user has to run next the command ftype with the string output after the equal sign to get displayed the registered shell command for opening files with file extension .nfo which is here UltraEdit.

ftype UltraEdit

The output for this example is:

UltraEdit="%ProgramFiles%\IDM Computer Solutions\UltraEdit\uedit64.exe" "%1"

All the hexadecimal bytes in the UTF-16 Little Endian encoded registry export above become now readable in this output. hex(2): in the above export is the type of a registry value of type REG_EXPAND_SZ because of the string value contains the environment variable reference %ProgramFiles% which Windows has first to expand before getting real string. The shell open command could be registered also with a string value of type REG_SZ if the string does not contain an environment variable reference. Most shell open commands for file types use REG_SZ as string value type.

The Windows command ftype cannot be used to change the icon associated with a file type. It does not even register which file contains the icon for the file type.

A user should execute therefore next first the following command line with the file type string UltraEdit for this example.

reg QUERY "HKCU\Software\Classes\UltraEdit\Shell\Open\Command" /ve

The user knows the file type registration was done only for the current user if there is the same string output as before on execution of ftype. Otherwise there is output the error message:

ERROR: The system was unable to find the specified registry key or value.

The user should run in that case the following command in the command prompt window:

reg QUERY "HKLM\Software\Classes\UltraEdit\Shell\Open\Command" /ve

Now the user should see the output as before with ftype and knows that the file type is registered for all users of local machine. In this case the user should close the current command prompt window and open a new one with Run as administrator and use the next commands with HKLM instead of HKCU from within elevated command prompt window.

Let us assume next the file ue-icon.ico offered for download by hugov exported with Resource Hacker (really good free tool often used by me) from UltraEdit executable of version 2022.2 containing this icon file in its resources is stored by the user in the directory %ProgramFiles%\IDM Computer Solutions\UltraEdit (using elevated permissions of a local administrator). Then the user has to run next in the command prompt window either

reg ADD "HKCU\Software\Classes\UltraEdit\DefaultIcon" /f /ve /t REG_EXPAND_SZ /d "\"^%ProgramFiles^%\IDM Computer Solutions\UltraEdit\ue-icon.ico\""

or

reg ADD "HKCU\Software\Classes\UltraEdit\DefaultIcon" /f /ve /t REG_SZ /d "\"%ProgramFiles%\IDM Computer Solutions\UltraEdit\ue-icon.ico\""

The first command adds the default icon string as expandable string containing the environment variable reference %ProgramFiles% while the second command adds the default icon string as standard string with %ProgramFiles% expanded already by the Windows Command Processor before running %SystemRoot%\System32\reg.exe.

The fully qualified file name of the icon file can be whatever is wanted by the user. This is just an example.

It is necessary to restart Windows to see the changed icons for the file types in Windows File Explorer as the command reg does not send an appropriate message to all running instances of explorer.exe including the Explorer instance running as Windows shell with Windows desktop, Windows Start button and Windows taskbar as visually visible graphic elements to inform them to update the icon cache.

There are of course also other methods to change the default icon for a file type like running Registry Editor as administrator on having permissions to do at all and edit the default icon registry string value with Registry Editor or using graphical interface. But all the other methods depend on version of Windows and which permissions the user has which is the reason why a described the change of the default icon using Windows commands which every user on every Windows can execute.

I just updated and find this new icon startling - I'm on the autism spectrum so I am admittedly very "rigid" in how my interface works - but for me the application icon being different, I don't "see" UE running in my taskbar be cause for 25+ years I've gotten so used to the classic icon.

I'm going to try and suck it up for now and see if Mofi's extensive reply contains any advice for me to maybe get it back but for me it's not just the file associations - it's the app icon itself I need to fix because .. this new one is horrible

From a design perspective, it's ugly, but it's my "neurodivergent" brain which is really unsettled by the change" which is my problem, not yours - but yeah ...

Hopefully like with the horrid Ribbon UI, there is an easy option to go back to more classic/standard things.

The application icon itself is taken from the first icon resource in the executable (uedit64.exe) or its resource DLL (ueres.dll). That icon can be changed only by using a tool like Resource Hacker. The problem nowadays on making changes of a resource in an executable or resource DLL is that the also embedded certificate with the hash for the executable / resource DLL with a signature created by a certification authority becomes invalid by such a resource manipulation as the hash changes. That does not make the executable / resource DLL itself invalid, but Windows could warn the user on starting the executable about the invalid certificate and the user has to decide if it nevertheless trusts the obviously manipulated application or not.

I could find out that with replacing icon group 2 in ueres.dl with Resource Hacker results in getting the icon as stored in ue-icon.ico now being inside the resource DLL displayed on the Windows taskbar and in title bar of the UltraEdit application window. Windows 7 showed no certificate warning. I have not checked up to now if Windows 11 22H2 would show a warning.

I saved the UEStudio v2022.2.0.52 main application icon resource with Resource Hacker into the attached file UEStudio.ico.

Note: Which icon is used by default by Windows for associated file types, for the icons of shortcut files, in the title bar of main application window, in Windows taskbar for the running application, in system tray on using the option to minimize to system try, etc. is defined by which icon group (set of same icon in various dimensions) is stored as first icon group in the resource of an executable. No configuration setting in UltraEdit / UEStudio can change that as far as I know.

All users unhappy with the new main application icons of UltraEdit and UEStudio should inform UltraEdit support by email about that. I am sure the main application icon is changed back if many users do that.

I like the icons of UE/UES prior v2023.0.0.40 also more than the main application icons of UE/UES v2023.0.0.40. But that does not bother me anymore after some weeks. I am getting used to the new look of the icons, perhaps because of seeing it only in Windows Start menu, on the Windows taskbar and in the title bar of UE/UES. I use Total Commander and not Windows File Explorer and have configured in TC to show all files and directories just with standard icons as also configured in UltraEdit for the File explorer view.