Please make AudioProcessor::changingParams available in Release Builds, so anybody can use it and avoid duplication of code
It's internal code used for debugging - I wouldn't want users writing code that depends on it, that's why it's private.
Why not, a parameter can be changed a several ways, a fader, a label, automation etc. I need to store the information if a gesture has been already sent, so i will just duplicate the functionality.
Then I think the best plan is for you to duplicate it.
When writing a library, minimising the exposure of internal implementation is a really important principle to be strict about. The more code we make accessible for users to tightly-couple their own code to, the harder it becomes for us to ever make changes or improvements.