TYPO3 Core

Issue #32701 made it possible to use custom postprocessors in the form extension. But these custom postprocessors can only be configured by typoscript for there is currently no way to load a configuration interface in the form wizard.

To load a configuration interface do:

(1) Register a Javascript class that extends TYPO3.Form.Wizard.Viewport.Left.Form.PostProcessors.PostProcessor as xtype typo3-form-wizard-viewport-left-form-postprocessors-{customName}

(2) Configure PageTS to show the custom postprocessor by adding your postprocessors name to

mod.wizards.form.defaults.tabs.form.accordions.postProcessor.showPostProcessors

mod.wizards.form.defaults.tabs.form.accordions.postProcessor.postProcessors.{customName}.showProperties

The second step is easily done, but to load the Javascript class, a hook in tx_form_View_Wizard_Wizard is necessary.
In tx_form_View_Wizard_Wizard->loadJavascript() additional Javascript files should be loadable.