Yes, sorry about the video quality, it was a quick demo on my mobile to show that each way selections between Genos Registrations, and Songs in Forscore, can be achieved. It's clearer on a PC screen.
This is what I do in Forscore v10.5, Maybe a different layout in v12?
I use the Yamaha MD-BT01 bluetooth adapter in Port 2 (B), which I personally find is way more stable in OnSong than Port A, and this reflects in the numbers in my following example.
You need a midi template and I find it best to start from the empty MIDI OFF template in Midi Presets.
On the System tab page 2/2 I have ON for System Exclusive Message Receive, the other 3 entries are all OFF.
On the Transmit page I only have one entry - Part 'Song CH1' Channel 'Port2Ch2', everything else is Off.
On the Receive page I have all 16 Port1 Channels set to 'Song', and under Part, Port2Ch1 set to 'Keyboard'.
Save the Template and for me this allows OnSong, Forscore, VanBasco's Karaoke Player playing through the Genos, and Chord Tracker.
On the Genos, Registrations must be numbered consecutively 001, 002 etc
In Forscore - Suitcase Icon - Settings - Midi Network - Scan - put a tick against Genos when its' found.
Load a song in Forscore, tap on title, click midi tab:
Click SEND, click on +, select Program Change from the menu. In the 4 boxes Chl-MSB-LSB-0-127 type 1-0-9-0 (if for example 009 is the Registration you want to select - enter in the LSB box, not the 0-127 box).
Click OPEN, then on the + sign, then on 'Learn' from the menu, then on the Genos, open the Regist Bank page by holding down the Regist Bank Select + and - buttons, then touch Registration number 009. If it is all connected ok, you will see the Hex Codes read into Forscore and saved automatically.
I hope I've remembered to write down everything, OnSong works quite differently from a one line Program Change number in a midi file saved to each Registration. I see no reason why this couldn't also be used for Forscore, but I haven't explored that yet