I mean if there is a GCD between Ferocious Bite (has a GCD) and Regrowth, then you will need to press the button two times for it to cast Regrowth
I guess you could use ( Still need 2 button presses )
/run SetCVar(“autounshift”,0)
/castsequence reset=12 Ferocious Bite, Regrowth
/run SetCVar(“autounshift”,1)