OK, I think see your problem Marc. Hover-Hold "H" is only for keyboard players, it doesn't work if you use a Joystick. You want Stable-Hover-Hold "L-Shft-H" if you are using a Joystick. There is a difference buried somewhere in the code, but I haven't gone looking for it.
"L-Alt-H" is for Altitude-Hold, which uses "L-Alt-J" and "L-Alt-K" to adjust the height setting, just like it says in the manual. I expanded "L-Alt-J" and "L-Alt-K" to ALSO adjust the height for Hover-Hold and Stable-Hover-Hold.
Important: Use L-Alt and L-Shft only, the R-Alt and R-shft don't work.
The speed limit for engaging Hover & Stable-Hover Holds is 40 knots. I don't know how fast that is in Russian units. I'll check it again in the code to see if I missed something there.
Altitude-Hold doesn't have a speed limit, just for clarity.