Well, not everybody can compile the firmware, which would be needed to add your own templates

I can't do it
As far as the trainer template is concerned, I am using a different approach..
I want to detect only the Ail and Ele sticks.. The master has always control of the throttle at this point.. My Son is just starting
L1 |v|>val Ele 4
L2 |v|>val Ail 4
L3 OR L1 L2 (This combines the detection from both sticks)
L4 1-shot AIL 0.2 (this prevents giving control to the student when AIL switch is just turned ON after I pressed the trainer switch. This is due to the way the Latch switch works. It will force it OFF..)
L5 OR L3 L4 (stick detection and L4 to be used to turn the latch switch OFF)
L6 Latch TRN L5 AND AIL (So, I give control to the student by hitting the TRN switch, but only if the AIL switch is ON)
L7 OR L6 TRN (Use this switch to control the trainer)
So, what this does is, if the AIL switch is OFF, the Trainer is operated normally by the TRN switch, that means,the teacher hold it to give control, and release it to regain control. No stick detection.
When the AIL switch is ON, when you hit the TRN switch once, you arm the Latch switch giving control to the student. If you move a stick, the LATCH will turn OFF and you get the control back, until you momentarily hold the TRN switch again to give the control back to the student..
I like to know at all times who has control of the model. I don't really like the shared control approach. For that I would just use the "ADD" function instead of the "REPLACE" one in the trainer profile..
I prefer to have full control of the model to stabilize it if the student messes up. No doubt that getting the control back by just moving the stick should allow for a very fast recovery when learning to land for example.. Of course it needs testing..
João