SpellQueueTimer

Hello i'm kinda new on warmane realms and i'm playing a caster. I come from retail/classic and i find casting weird sometimes especially when i'm in heroism and i have to smash buttons kinda more.
In retail/classic i used to have AdvancedInterfaceOptions and there were that slidder about SpellQueueTimer which i remember i set to max to have a better feeling with casting (was 400).
I tried this command on the server : /dump GetCVar("SpellQueueWindow") and tried to set either /console SpellQueueWindow 0 or /console SpellQueueWindow 400 (which is the max i think) but it doesn't change anything. It always says empty value.
Anyone knows what i'm talking about ?

it seems like i have to mash buttons (what i hate) when i'm close to the gcd otherwise if i press key for the next spell while in gcd a bit earlier (even 0.0001 ms) the spell won't cast