How to convert to hexadecimal in Keil Studio Watch windows

On my side this works as expected. And your setting in the launch.json file looks fine.

Could you please confirm whether you can also see the 'Set' command being called in the Debug Console?  This would indicate that the command is actually being applied by GDB.

If not, then the issue is likely that the launch.json being modified is not the one used by the active workspace. I’m not sure about your exact folder structure, but please make sure you remove other unnecessary .vscode folder and are editing the .vscode/launch.json file under the currently opened VS Code workspace, rather than another project directory.

On my side this works as expected. And your setting in the launch.json file looks fine.

Could you please confirm whether you can also see the 'Set' command being called in the Debug Console?  This would indicate that the command is actually being applied by GDB.

If not, then the issue is likely that the launch.json being modified is not the one used by the active workspace. I’m not sure about your exact folder structure, but please make sure you remove other unnecessary .vscode folder and are editing the .vscode/launch.json file under the currently opened VS Code workspace, rather than another project directory.