I need to execute some logic in a Composer bot that is not possible to do in Adaptive Expressions, so I went ahead and followed this instructions to create a custom function that I'm suppossed to be able to call from an Adaptive Expression in composer.
Then I added the function name into the settings like it's indicated here:
https://docs.microsoft.com/en-us/composer/how-to-validate#custom-functions
Running from composer or from the cli I get the same error: Application startup exception System.Data.SyntaxErrorException: {NAME_OF_FUNCTION_HERE} does not have an evaluator, it's not a built-in function or a custom function.