I am not quite if I add it a crescendo to the middle between the 2 staves (G,F) that will be applied to both notes on both clefs ? Any ideas ?
Yes, dynamics applied to the top staff of a grand staff system will apply to both by default.
I think you can use alt-enter to enter voice-specific dynamics. (Both staffs being different voices by default).
I am using that dynamics for piano . Can you explain please how can I use alt-enter to enter voice-specific dynamics?
If you enter dynamics vis the shift-D popover, confirm not with enter but alt-enter