Pipeline builds are able to record Jenkins fingerprints and those can be accessed with the Web UI of a particular build.

However they are not accesible via Jenkins api, which prevents using them by any automated tools.

The reason for this is that FingerprintAction is not annotated with ExportedBean and the api does not publish it directly. Instead AbstractBuild has a method getBuildFingerprints which is @Exported as fingerprint with visibility -1. This way the developer excludes them from standard view but it is accesible via tree parameter. See https://issues.jenkins-ci.org/browse/JENKINS-10481 for reference.

Since WorkflowRun does not inherit from AbstractBuild it does not inherit this method and the fingerprints are not accesible.

Therefore could you please just add a similar method to WorkflowRun to make fingerprints accessible? 
The alternative would be to make FingerprintsAction exported directly, but maybe this is not wanted.