One thing that is super convenient is having a template for cone, sphere, line and cube spell area of effects. I have seen this done “ruler style” in which you select the shape (cone for example), click on the point of origin, and then drag from that point to expand the size and to select the direction the spell is going in, with a measurement reflected on the side (e.g. so you can expand the cone to 15ft for burning hands).
Visually making it a translucent colour and deletable by the players after casting would be dope as heck.
Added bonus would be if it could highlight creatures that are caught in the range of this area of effect