How to assign the action \ "to throw a grenade \" on a separate button? (Fallout 4)

The fact is that by default, several actions are assigned to one button to throw a grenade, melee and another devil bald. And at a critical moment, when a crowd of enemies is running at you, you start to frantically press this button (default l alt), the character starts waving his hands. And it is unclear whether I am pressing the button incorrectly or the grenades are over. I need to assign
one specific action to a separate button (scm or G) Throw a fucking grenade and nothing else! How to do it?