Yes. Ketron Germany published a german manual. The manual shows how to configure SongBook+ and Ketron keyboards to automatically open a registration on the keyboard when a song on SongBook+ is opened and also to open a song in SongBook+ when a registration on the keyboard is selected:
German manual download from here: Anleitung_AUDYA_Songbook.pdf
English translation see attachment.
The manual is a bit outdated and contains screenshots of an old version of SongBook+.
An important difference to the current version of SongBook+ is, that the settings of SongBook+ are now contained in the app itself (see button with gear wheel icon) and no longer in the general "Settings" app of the iPad.