Hello @dav1 ,
Thank you for your question on the NXP Community!
MCXN236 is supported in MCUXpresso Config Tools. Support for the MCXN2xx series (including FRDM-MCXN236) was introduced in Config Tools v15 (bundled with MCUXpresso IDE v11.9.0) and continues to be available in the current v26.06.
The error you are seeing is most likely related to how the project was set up. Config Tools needs to be launched from within a proper SDK-based project in order to correctly identify the device and generate initialization code, simply downloading processor data via the Data Manager is not sufficient to enable full tool functionality.

When creating a new configuration in the standalone Config Tools, we recommend selecting a project type that is associated with an SDK or a specific toolchain, rather than a processor-only configuration, to ensure the device is correctly recognized.

Additionally, please note that the standalone Config Tools is not intended for use with MCUXpresso IDE, if your development environment is MCUXpresso IDE, please use the Config Tools that are integrated within MCUXpresso IDE directly. For other supported IDEs such as IAR Embedded Workbench or Keil MDK, the standalone Config Tools is the appropriate choice. If you are using MCUXpresso for VS Code, Config Tools is also built in and does not require the standalone version.

We hope this helps! Please feel free to follow up if you have further questions.
BR
Celeste