Thank for your enquiry and for illustrating your use-case
You could override the JavaGenerator.newJavaWriter() method and return a JavaWriter that is initialised with @formatter:off. Then override also JavaWriter.beforeClose() and generate @formatter:on in that method. This way, you can add these markers to all generated jOOQ classes.
Of course, post processing might be easier (e.g. when using Maven to generate code) and more forwards compatible, so I'd recommend that if possible.
I hope this helps,
Lukas