Hello Christian,
Hauptwerk doesn't currently (v4.2.1) have any easy means for end-users natively to add their own graphical console display pages/layouts to existing sample sets, I'm afraid (although we do hope to include such functionality in the longer-term).
As long as the sample set's licence allows it, the options you have are:
1. Create a new organ definition (ODF) from scratch for the organ using the Custom Organ Design Module (CODM). Your CODM ODF could then have any specification you wanted, and with any console layout/graphics that you wanted. The CODM user's guide is on the Help menu in Hauptwerk. The CODM is designed to be reasonably easy for moderately technical people to learn and use, but it does require some 'programming' in XML files. A sample set producer might possibly have included a ready-made CODM ODF versions with his/her sample set for you to use as a basis for your own modifications (although not many actually do that, as far as I know).
2. Make a copy of the existing 'full-format' (non-CODM) ODF and modify/extend it yourself. That could potentially be very complex (also depending upon the complexity of the original ODF), and it isn't something that we can provide any help or support with, I'm afraid. (We only provide support for the 'full' ODF format to major commercial sample set producers, due to its complexity.) However, if you do want to pursue that option then we could email you a copy privately of the documentation for the format; please let us know if you'd like us to do that.