@JeremyECrawford is the action to maintain a Witch Bolt the Cast a Spell action? Could I cast misty step on the same turn I maintain it?
— (((Em Wizardshark))) (@DylanRubini) June 28, 2016
You use the Cast a Spell action to cast a spell. An action in a spell that's already cast is an ad hoc action. #DnD https://t.co/uIURQEw0NC
— Jeremy Crawford (@JeremyECrawford) July 21, 2016
I think what you mean is if it will cost a new spell slot? If so then no its a concetration it does however take the regular action.